People like niceness from other people,
it's just that if somebody is always trying to please you, you think that they have no life of their own...
I remember back in high school there was this really unpopular "nice guy" who wanted to be friends with everyone in the school. Then one day in class he was sitting next to me, and he had an itchy thigh, so undid his belt to scratch it, so I started a rumour that went around the whole school that he was masturbating in class.
He was quite stressed about it, but I told him "just don't worry about it, the more you react the more they'll hassle you" but he didn't pick up on it, and later on he told me "YOU RUINED MY LIFE!"
Now his facebook status's say "I am working overtime again, because it is fun and there are always ways you can add value to your company!"
I feel a bit sorry for him
Other than that, I can't think of any annoying doormat nice guys, all my friends are nice guys, but none are "nice guys"
But if I was a girl, I'd probably have some annoying nice guys hitting on me...