MrFlibble: "Fair" is one set of coins (however many the Faucet is giving out at the time-- hopefully, bitcoins will continue to become more valuable, and I'll give out fewer over time...) per person.
I like the postcard idea, although I'm not willing to type in bitcoin addresses written on postcards!
Hmm... any stamp collectors here? Paying people bitcoins to send you postcards (with stamps on them) might be really fun...
And re: using OpenID instead of a Google Account: that'd be easy to implement, but way too easy for cheaters (who can just be their own OpenID provider and give themselves as many OpenIDs as they want).