Have you ever tried to learn a language from a native speaker? How about being taught a sport by someone with incredible natural talent? I had a college roommate who was nearly a savant when it came to math, but he couldn't explain to anyone how he did it.
In the same vein, most of the great baseball managers were rather mediocre players. The reason was because they had to learn the sport, make mistakes, and work really hard to even be half as good as the next person. That meant spending twice as much effort to figure out how to gain any advantages they could...all through learned and practiced behaviors--behaviors they can actually teach.
It's hard to teach someone when it comes naturally to you.
For college students, much of their online behavior just seems natural--having grown up around computers and the internet. They don't think about how they participate in social media... they just do. Ask them to participate in social meda on behalf or because of a brand, and you'll get a blank stare--despite the fact that they've got glittery corporate logos plastered all over their MySpace profile.
"You want me to ask people to use this?" That's what you'll get when you put a service or product in their hands. They don't understand that the subtleties of what they d on walls, in chat, over sms is what marketers wish they could capture in a bottle and activate with a single click.
So if you think you're going to go hire a bunch of college or high school kids to push your brand around social media, think again. You'll probably find them to be a lot less adept at it than you'd expect, even though its something they do everyday.