I do think there are kids who are driven to know that next level of something like math or science to the point that it makes sense to go to the college level to feed that drive. And if you have the ability to do that and the kid wants it, that sounds fine to me.
But I agree with Kriston that there are tons of things that are really cool that are never taught in typical K-12 or even most colleges. If you have a kid who is ahead in the typical academic subjects, then there is way more flexibility to explore those things. I know of a camp that teaches animal tracking and outdoor survival skills. I know of several tall ships programs that teach kids how to climb masts, rig sails, and generally become sailors. There are achaeology programs that let kids go on digs. In a couple years, we plan to send DS to Central America to stay with Spanish speaking friends where he will go to school and help with the family's small store. All of these programs allow kids to actually use some of their school knowledge, but put it in a context that makes it "real world" applicable and gets them connected with a broader range of other kids. For our family , it makes more sense to explore these things than to forge quickly ahead into college level material.
But I have a relative who graduated college at 18. He is brilliant, successful, and happy. For him, early college was clearly the right choice--he just had to know about physics and college was the best place for him to get the answers he craved. It all comes back to knowing your kids and knowing your options.
