I'm totally against this, if you're busting a party that's fine to ticket the kids. However, busting them how many days, weeks or months later for a crime that can't actually proved happened. Holding a beer is not drinking a beer. Maybe the kid did slip up and admit it, but do we really need to question a kid about underage drinking? It is a total waste of resources, the cop has to find the kid, send the friend request, see the pics, sure that would take much time at all. However, then there's the arresting or ticketing process, sending this kid to court, wasting the court's time, all for what a $150-200 fine?
The underage drinking laws are ridiculous anyway, all it does is add to the stupidity of kids getting drunk because they're doing something bad. Especially when it's on a college campus, since more often than not the kids aren't going to be driving since it'll be a dorm party or off campus house close enough to walk to. I don't think I ever drove or got a ride to a party when I was in college, since it was so much easier to just walk.
That said, I do think kid's these days are too stupid to be using things like Facebook and Twitter because they feel the need to broadcast every single bit of their life on the 'net.