In games that are designed for multiplayer but have a single player component, I can understand, but I do get a bit annoyed when I have a single player game with online trophies when I don't like to play online too much. Most of the big FPS shooters, sure. Assassin's Creed Brotherhood? No thanks.
I think Uncharted 2 had the right idea with keeping the multiplayer trophies required for plat really simple, but I'll admit those could have been better designed to make me put a little bit of time in. If I'm required to have a ton of skill, rely on other humans, or play the multiplayer for weeks on end to get a platinum trophy, there just isn't much enjoyment there for me. I still consider myself lucky for getting 4 team wins in a row on Red Dead the first time I tried for it.
