People aren't partying/drinking more because of Facebook and other sites...it's just more in your face now than it was before.. Years back there wasn't such an instant way to share what you were doing, now there is. That's the difference.
Like I've said, I don't think there's really a way to prove it. I'm not sure if there's been studies on this yet. It's more of a theory.
Think about it though, if you go through a news feed, you see all the check ins, images of people doing things, most will be "tempted" to do the same eventually. We crave consumption.
I think everyone has "self invited" themselves at one point. You see so and so checked in, so your like "fuck it" I'm going to head over there and check it out and as a guy you might be even more tempted to join if you notice there's girls you know or recognize. Oh what a coincidence we are at the same place. hahah bullshit!
So what I'm saying is there's just more ways to go about meeting people now because of social networking. It's become effortless, it comes to you on your phone, email, heck even car. Therefore I think there's a correlation with more drinking, partying, buying shit or just doing more in general. I just think we've been bred into competition. Heck, our economy functions off of Capitalism which is the foundation of competition. We are easily tempted and I think it's at its greatest point ever.