Although the value of online sarging can be disputed, the fact that a decent amount of social interaction takes place in colleges, proves that their can be a use. for example, when getting someones name or number.. never add them. if your in class give them your name and have them add you. in the real world you take numbers not the other way around. but online 'adding them' on facebook gives them them the dominant position.
If you do choose to add someone you don't know on facebook or myspace, you could go with a pretty easy multi line opener ive used many times.
you: "Hey, is this you? your cuter then my friend said. hes lucky to have you

"
hb: huh? or "whos your friend?"
you: oh shit... wrong person.
hb: ...ah lol. well should i click deny then?
you: lol, well it depends if you want to be my friend or not.. thats on you
This kind of thing is a hit or miss but when online you can really do this to a ton of people at once. ive found that it works with the first person most of the time.