Facebook and twitter both are good social networking sites, which is one of the best source to getting traffic.
Social Book marking is important for any website because it can generate traffic i suggest for you face book,twitter,try to work on do follow link its very helpful.........
Facebook was initially intended for college students ..it branched out and now allow everyone membership near about 500 millions members...
maybe, has to narrow the question which for what area or niche? but in general, the most powerful should be fakebook.
I think this is relitive. No one can really tell which is the best. Each one has its pros and its cons, so each one is pretty equal in my eyes.
Facebook hands down. It used to be myspace, but as the generation grew up, they shifted to a more professional looking social site aka facebook. We should make a new social network for when this generation grows old. lol