What is the effect of social networking sites to your health(emotional, physical, spiritual)?

[aRwiN:)]

Facebook, Twitter, Myspace and other social networking sites are now a trend today. For a normal TEENAGER, what would be likely the effects of Social Networking Sites to your health(emotional, physical, spiritual)? Please elaborate your answers... Please specify...if you have experiences,,,you can share it here.
Can you please help me out?

Thanks for those who answered

[Billy Bob]

stay away from social networks! they will turn you into a stalker.

[Saurav Kumar]

if you are using the social network the just be on yourself and with the persons you actually know
show about you to your friends if you want to show otherwise don't show
it is good to stay out of these

[jeff j]

If you use it instead of developing real-world friendships, it will be detrimental to your health.