I wasn't saying the buyer wouldn't have to share his wallets address normally. Of course the buyer must share his wallets address, but the caveat is that he mus

I wasn't saying the buyer wouldn't have to share his wallets address normally. Of course the buyer must share his wallets address, but the caveat is that he must do so publicly so that everyone can see that he owns that wallet, so that everyone can see that he received that money. If the buyer didn't reveal his wallets address, he could claim that the seller owned the wallet where the bitcoins were transferred, or that they were transferred to someone else. There's no way of proving otherwise unless the buyer did something to tie the address to himself. (he bought some movie tickets and the theatre disclosed it was him, for example.) Of course, that's looking at it from a pragmatic view. As others have explained, payment services don't care at all about what's actually happening, only that what HAS happened fits protocol. So this won't matter until the world has come to terms with crypto-currencies.