Facebook users...

get lower grades in college when compared to their non-user peers. Interesting correlation but not necessarily causative.

I will tell you this from a professor's perspective: texting, Twittering, updating your Facebook page or otherwise surfing the net on your laptop and generally fidgeting with your cell phone while in lecture is rude and immature. Most students that engage in these inappropriate behaviors in class usually sit in the back of the lecture hall, which typically correlates with low grades. I always wonder who is paying their (soon to rise) tuition?