If you have interest and motivation, college can help you out. If you're aimless at 30 and hoping college will magically pair you with a career you think you deserve, have fun at the Occupy Protests praying someone nulls the debt you signed up for.
Do people go to college on a lark in their 30s? That's what you do straight out of high school - or rather, you are going because someone expects you to or you have nothing better to do. Most people I know who went to college later in life did so with a focus on learning a specific, marketable skill and have done well for themselves.
The exception to this would be people who get snookered into some shitty online or for-profit school. Those are pretty much garbage.
I was one of those kids who went to college because it seemed expected of me after high school. I will say that it broadened my mind, made me a more critical thinker, and by the end (too late to help my GPA) I did learn to do work well and grow up a bit. I enjoyed the time and I will reiterate what others have said about there never being another place easier to meet girls. That said, I would probably do shit differently if given a do-over.
I went to a middling school and had a bullshit major. My degree has not helped me acquire work in any way besides allowing me to check the box that says B.A. on the application.
My sister went to an Ivy League school, got a bullshit degree and now works in Manhattan for hedge funds making bank. So there's your best option if you haven't fucked up high school yet (and let's face it, if you are on here you probably already did).
My wife went to a state school in her late 20s and got a degree in a specialized field for which her university had a strong job placement program.
Were I to do it over, I would try to take one of the latter routes. Hopefully try to work in some travel (study abroad, etc.) because once you get responsibilities that shit just ain't happening. I guess one last tip would be to get a serious internship and do it well because in a lot of fields that can be the easiest entrance to future real work.
I'm not saying college is unequivocally better than some other stuff like learning a trade but I do concur that one should avoid the I'm gonna totally fuck off throughout my twenties because it puts you in a shitty spot by your late thirties and beyond.