I may have a slightly different viewpoint here. Not as a mom for a change but as someone who did get put into college early. I went to a private school and when I took my Iowa tests they told me that I couldn't learn anything else from them. I was 14 at the time and state law for where I was said that I had to have approval from the principal and one other principal from another school, a member of the board of education and the dean of whatever college I decided on. I also had to go to one year of highschool (age15) at the same time as taking college level classes. I'd already taken my SAT's when I was 12. These days that and a cup of coffee get me less thirsty.
The pros:
I LOVED learning and the challenges that college gave me. I'd done homeschool, private school and public school and this gave me something that I'd never learned before. A chance to learn who I was,how to be more independant and stretch my own brain even more than I was used to.
I went part time for a lot of the time and was able to get a scholarship when I first started just because I was young. I think it was through the Elks lodge, but it was sponsored by a coworker of my moms'. I worked my way through the rest of my classes by doing tutoring and some TA work in the highschool (it was legal as long as I was in college slightly more than half time). I got a full time job by the time I was 18. Good work ethic

Most of the basic classes do/did transfer to other colleges.
I had the chance to meet some very interesting people going through a community college that I would never have had the chance to meet otherwise.
The coolege administration knew my age and were easily impressed by it so I loved the kudos I always got from that (is that a good thing?)
The cons:
Usually I downplayed my age to the profs since the few who ever knew my age seemed to believe that I really should be in highschool even though I was getting A's and B's in their classes.
Dating didn't happen. I was around others who were my peers in every other way except that they were going through a more mature stage of emotional development than I was ready for (kind of). Basically I was way under 18 and I went to a community college where one of the guys I'd been tutoring (who knew my age, but didn't tell anyone) was getting ribbed for being the baby of the classes at 18.
The biggest thing for me was the burnout factor. I'd been having to go part time for a really long time and it didn't seem to be getting me anywhere. I had to take some time when most people would have been graduating and go work/live in the real world to figure out what I really wanted to do. I finally have a much better sense of who I am and have gone back to college (again!). This time I'm actually sticking to it though and getting my degree with a plan as to what I'm going to do once I've got it. I should note that I did know 2 other kids who were going to the same college I did. They also suffered from burnout. In their case it was because everyone put a lot of pressure on them to be perfect and always do well in their classes. Stress like this caused one of them to have an ulcer at 13.
Strangely enough I really wouldn't change anything that happened (expect that maybe I wouldn't have dropped out from college when I did the first time). Going through highschool and college at the same time that first year I came to understand exactly how differently highschool students and college students are treated. In highschool (even the private school I was in) you tend to get into trouble for asking questions and being outspoken. In college it is not only encouraged, but expected. I'm now a very outspoken person when I want to be (ok, sometimes pushy) and it usually gets things done. I'm 32 and have 26 acres that will be mortgage free in 3 years because I learned to plan when I was young and that sometimes you have to be willing to know what things you are willing to give up if you really want something badly enough (I lived in a tent for about a year on the property). I've met people that I will never regret meeting, and because I was so young it left an even deeper mark than I think it would have otherwise.
I'm not sure that a four year college is right for someone who's very young (I took some classes at a 4 year colege when I was very young too). A community college is more likely to have adult students who have more life experience and that is really the best thing to take away from it all. For most students though I think that taking dual credit classes through a college is probably the best way to go.This way they can have the social interaction they are already used to, it helps ease them into the college rythym (every college has it's own), they still have parents to fall back on if it's needed for moral, emotional and financial support and they may be able to focus more on school and finishing it once they have a better idea of who they are.It also means they can take college part time while taking other classes at home or doing volunteer work or whatever may help in their own self discovery. Everyone deserves the chance to enjoy self discovery. Everyone also has their own path to get there.
This is starting to sound kind of windy. Sorry about that. This is part of what goes into my own reasons for homeschooling and it's 5 in the morning here (been up since 4). I hope some of this gives a different perspective on things. Both the good and the bad. If you want a more coherent answer to any questions I might be able to answer you can feel free to IM me.
LeBoof