Between CLEP, AP, community college, and the right summer classes, a really bright kid could probably graduate college in 2-3 years in certain majors.
I did my bachelors in 4.5 years though 1 year of that was doing an internship in the middle, so I guess technically 3.5 years. I did that by clearing 11 hours through clep, 6 through AP, took 9 hours at community college. If I had done CLEP earlier and had settled on my major to begin with, I probably could've done it in 3.