Some of them do, but how many?

Most of those businesses did not adopt bitcoin at all.  They merely agreed to accept dollars from the sale of bitcoins that people already had, including cheap coins that had been dormant since 2013 or earlier.

Bitpay expansion does little to increase adoption; it chiefly makes it easier and more tempting for long-time investors to sell some of their coins on the open market.

And they have no reason to do so.  Just as they have no reason to speculate or invest in Apple stock or rare stamps.

I am not sure what you mean, but: from all I have read, I am quite convinced that the November rally was entirely due to demand in the Chinese exchanges.  Ditto for the December crash and partial recovery, the decline from February to April, the stagnation in May, and the the mini-rally a couple weeks ago.  Not sure yet about the current decline, but it seems to have coinided with a new push to cut out the remaining channels of yuan deposit to the exchanges.  

I don't know how many coins are still in the hands of Chinese speculators and investors, but, if the markets there were to close and those coins returned to the Western market (which they probably would, since speculation seems to be the last significant utility of bitcoin in China), I am quite convinced that the price would drop to somewhere between 80$ (an estimate of where it would be if China had never entered the game) and 350$ (which it briefly reached after one of the PBoC scares).

As for Mr. Lee's claims: his exchange BTC-China used to have the largest volume in China until the December crash. Since that time it has become insignificant, while Huobi, OKCoin, and the other Nameless Ones became dominant.  (Huobi in particular seems to have bumped its volume just when BTC-China suddenly lost theirs).  I watched that video and heard the claims, but did not see the evidence. His being elected to the board of the Shrem Karpelès & Friends Foundation, together with Mr. Pierce, did not help convince me.

Not at all! I don't know before December, but since then the flow of yuan into or out of the mainland China exchanges was quite restricted to people with accounts in Chinese banks. 

Thus the supplies of dollars+euros and yuan available for bitcoin trading are basically isolated from each other, except perhaps for some traders.  But bitcoins can be freely transferred between continents, so if there is demand in China, that demand will be immediately felt in the West.

This claim has been repeated thousands of times in the bitcoin media and forums, but never with substantive evidence.  I have found hints that some of OKCoin's transactions (but not Huobi's) may be fake, but those won't reach 10% of that site's volume.

A sufficient explanation for their large numbers is that the Chinese sites charge zero fees, so they attract more clients and each client generates more volume.  That is not "fake volume".  Moreover, as several sources pointed out, China already had a large population of amateur market speculators -- something that seems absent in the West.

On the other hand I suspect that a large fraction of the volume at the "Western" exchanges is merely arbitrage with China.  If arbitragers generate (say) 25k BTC of trade per day on each side of the "frontier", it would be 50% of the Western volume but only 15% of the Chinese one, so the disparity would only increase.

Considering only the major exchanges listed in bitcoinwisdom's menu (all in kBTC):

BTC-e 10 + Bitstamp 17 + Bitfinex 25 = 52
Huobi 57 + OKCoin 97 + BTC-China 7 = 161

If you were considering only About the Chinese exchanges, beware that there are another two or three big ones, not listed by Bitcoinwisdom, that may add to 50--100 kBTC/day.

In the "West" there is also LakeBTC that was about as big as Bitstamp in volume, las time I checked.  Bitcoincharts may list them.  There are many others, but I do not know of any large enough to make a difference.

There is also substantial volume of BTC against other cryptocoins, not included in the numbers above.

Bitpay may be considered to be a one-way exchange cum payment processor. But their daily volume must be modest too.

EDIT: quoted poster edited the amount from 164k to 64k.

Currently it seems that, for many bitcoiners, just owning coins is all they want from life. But, in that distant future we are considering, that will be sort of passé:  people will presumably want to spend their bitcoins too. 

Suppose you buy a fancy car with the bitcoins from those "side jobs".  The tax detectives will know about the payment, and will link it to you, from the dealer and other sources.  They check their databases and discover that the payment did not come from any of the addresses that you declared in your tax forms.  What then?

Mixing won't help, quite the opposite. The tax office does not need to find out where your extra coins came from; it is you who will have to explain -- and prove -- to them that you paid the tax on that extra income.

Ditto for coins from "dirty" jobs -- if the tax guys suspect that your extra coins may be related to illegal activity, they will warn the police.  Then it will be you, not the police, who will have to explain -- and prove -- that those coins came from legal activities.

Note that the government does not have to catch every single tax evader.  They only need to catch and sternly punish enough of them to scare most of the other citizens into voluntary compliance. 

Yes, that's is the spirit.   ( A fellow government worker there?   )

Although the dialogue may have been more like:

FBI: We got some seized bitcoins cleared for auction.  You guys know how to handle that stuff?
USMS: Yes, no problem, the auction could not be any easier. Just send the coins, I'll email the address.
FBI: Good! Thanks, bye.

No more for bitcoin than for any other merchanise.  It is not part of their mission to make a profit from sales of seized stuff.

Why do people think that the FBI views seized bitcoins any different from seized cash, gold, stocks, etc?

The don't need any new ways.  Not paying taxes is already a crime, whether you transact in dollars, in euros, or in something else.  If you earn bitcoin and do not pay taxes on that, they can take your car and house and/or send you to jail.

Or do you think that they cannot find out about your bitcoin income?

If the incident happeneed 2 years ago, then there were no altcoins around at the time, were there?

There is as much fraud and embezzlement in academia as in most any other professions.  I know several cases in my own department and university that are much worse than that one, in terms of amount of taxpayers money pocketed illegally.

Bitcoiners should not gloat too much, though.  This may have been a healthy community of hopeful, honest, idealist hackers at the beginning, when bitcoins were worthless tokens in an obscure computer science experiment.  But, since then, all the crooks in the  world -- from the street vendor who sold fake hello kitty stuff, to the Russian mafia, and to Wall Street sharks -- have discovered bitcoin, fell in love with it, and immediately aimed their skills at it.  I sometimes doubt that there is now one bitcoin-related enterprise that makes money without swindling someone. 

Erm, how many thousand administrators are employed to keep the bitcointalk.org site running?
(There must be a few hundred working full-time on the avatar bug alone, I presume.)

Like the US House of Representatives (lower house of Parliament).

Right. Never mind.

But how can the pool check that the submitted (failed) hash is correct for that nonce, without redoing the work? 

Thanks.  By the way, how does the pool make sure that each member is actually trying out all the nonces that he is supposed to try?  If the pool software runs on the miner's equipment, it could be compromised and lie to the pool, couldn't it?

Right. "Mine workers" is not appropriate either because it is not them that do the work, it is their computers.  "Slave owners who rent their slaves to a mine" may be closer. 

It occurred to me that since the computers are now making money themselves, rather than being an instrument for humans to do valuable work, perhaps they should now be given full person status and citizen rights, while their human tenders should be relegated to the status currently enjoyed by pets and horses. 

I presume that the destination address in the reward payoff transaction, at the start of the block, is specified by the pool, not chosen by the miner -- correct?

The USD equivalent displayed on some charts (eg bitcoinwisdom) is computed from the CNY price by some CNY:USD exchange rate, presumably the official one, not necessarily up to date.  I have noticed that arbitragers apparently use a different exchange rate; say when the official one was 6.22, the Bitstamp/Huobi ratio, at "quiescent" times seemed to be consistently closer to 6.10 -- that kind of difference.  This "arbitrager's ratio" was itself fairly consistent, for days or weeks on end.  I will try to post a graph later.

Moreover, the Bitstamp/Huobi ratio was often well off the usual value whenever the price was changing very fast -- presumably because the arbitragers were unable to keep up.

Also, at Huobi the arbitragers apparently went to bed at night, like other clients.  Usually that did not matter because Bitstamp would be rather quiet at those times too. But if there happened to be independent activity at Bitstamp during the night (like there was a hour ago), Huobi would not pick up the change until waking up.

EDIT: clarifications