@def: No you misunderstand. I'm not saying "quit immediately at the first sign", I'm saying "if something really bother you that much then..." If you want to stay in, stay in, but this is the first time it's happened to the OP and he's already posted a thread about it. It sounds like it bothered him/her a lot.
Douchebags will be douchebags. This guy wasn't necessarily trying to get a free win, he was (as described) trying to "punish" the other player. In staying in the game, you're letting them grief you - that's what he/she wants. Why give them the satisfaction? Who cares if they get a free win? Whoopee-frikkin'-do. I like to win as much as the next guy, but not if it's a really irritating and frustrating game - that's not why I play dominion. Sticking it out in some kind of misguided idealistic stoicism isn't going to stop douchebags being douchebags. The other alternative is to not let it bother you, just open a browser and read some news while you wait.
If it did become common practice then well, maybe something should be done about it. But it's not right now. Yet already we're talking about wanting to do something about it. How about we wait until it's actually a frequently occurring problem (eg like drop-hacks in some games) before grabbing the pitchforks eh? People will be douchebags now and then, especially on the internet. Just deal with it.
@barsooma - I agree there is a big difference (though deliberately not ending it and toying with them is actually pretty damn obnoxious in my mind), but we've only had one side of the story. Maybe there were loads of opportunities? Maybe the other guy doesn't agree, maybe he finds it really really obnoxious to not end the game - who's to say our view is right? Why is it only us that gets to judge what behaviour is and isn't acceptable? Just because one guy posts a bit of chat from a game, I'm not going to instantly assume the accused is a completely reprehensible twat