Strictly-speaking, it is unnecessary for an entrepreneur, but I wouldn't be very keen to skip college (what's the rush to start your first business? Your career as an entrepreneur doesn't end at 30). The educational background will be very useful -- you can learn Rails, SQL, and the like on your own, but tackling true CS subjects individually is not something a lot of people can truly do. Going to college is also a great experience, from a networking and personal maturity perspective.
Well, I'm just saying that the number of people with the enthusiasm to really, deeply grok, say, the PCP theorem, Bayes nets, or the FFT in their spare time is quite small. Sure, undergrad CS is just a "warm-up act for the real thing", but a solid grounding in all those topics is a really useful thing for someone planning a career doing technology startups.
