hating facebook because of some of the people on it is silly, especially considering you just need to friend the right people - youre not exposed to every single person on there if i under stand how it works
if you hate facebook because of the layout, or you think it doesnt give you much privacy, or something like that that has to do with the actual site thats more reasonable
the same applies to any sort of social site that only shows content from people you follow/friend/etc, if you have to see everything posted by everyone(ie forums or imageboards) and most
of the community is bad then its reasonable to be upset about it