I see the OP's point of view though, despite everyone jumping on him for it
My sister spends copious amounts of time on Facebook, hours ever day. She gets grumpier and grumpier every time she does so.
There a study recently showing that the more friends you have on Facebook, the more stressed you are after being on it, so it can have a real impact on people. :/
Yes, she gets real mood swings from it as well.