Gavin Andresen - 2011-03-07 20:18:50

My question is:
Is it a bug (not to see the payer address) or there is no bug and I have to ask my customers to pay to my IP to be able to know the payer address?

There is no bug, but if you want to know one of your customer's bitcoin addresses (maybe you want to send them a refund?) you must ask them.  They might be using an escrow service like ClearCoin or, as theymos says, using a shared wallet service like MyBitcoin.