Are public networking sites like facebook orkut etc useful??

I don't know why generally people guys say that these websites are a waste. Well me being an net savvy guy, I say it’s useful so I thought of some points to strengthen my point, so here this goes:-

• It’s a way to network and meet new people.
• Well don't expect me to keep a record of all phone numbers and calling all my long list of friends from various schools I have attended (I had many), college and after college life etc I have been associated with.
• Find your lost friends, old friends, far away ones and maintain contact with them.
• For advertisers- (especially for adverts targeting specific net savvy audience or younger generation)
• Earning way for others (see various applications in FaceBook or orkut etc, its a goooood business).
• See what others are up to (sounds fishy) or make network groups etc.. kind-of time killing method. Anyways it depends on individual preferences and perception what he does with this info or meeting ground.

Well About WASTE of time-> well if you are not doing anything constructive then u are wasting time.. My personal point of view:- I don't like people sitting infront of these websites browsing others whole day and waiting for a scrap to pour in.

Anyways if you can think of any more points then add yours too.. :)