Texting girls from Facebook you dont know

Me and my friend were having a discussion(argument rather) about whether its ok or not ok/creepy to text a girl who's number you got on Facebook. I think it is ok provided you're using a good technique.

Say the situation is this: you recently added a girl who you thought was cute. Her number popped up in your phone. Is it ok to text her?

I would like everyones opinion in this

I think if your friends with her on facebook, it might make more sense to message her on it rather than to her phone. Phones are more personal and she would only expect people to phone/text her on it that she knows or has willingly given her number out to.