Jehan Ratnatunga, a 26-yearold Australian, thinks the best strategy for underwriting water sanitation projects in the developing world is to launch a nonprofit toilet paper company called Who Gives a Crap. Silly? Perhaps. But the idea proved just intriguing enough to earn Ratnatunga a spot as one of 25 fellows in the first-ever Unreasonable Institute taking place this summer in Boulder, Colo. Some 284 applicants from 46 countries vied for the chance to take part in this new social enterprise incubator. They first had to earn their way—and demonstrate their entrepreneurship chops—by competing for sponsors in a social media marketplace. Ratnatunga’s venture was one of the first to get funded, thanks to 228 sponsors who contributed a total of $6,500 to kick-start his idea. Daniel Epstein, one of four founders of the Unreasonable Institute, says the program is intended to fill two critical gaps facing many young social entrepreneurs: mentoring and access to capital. High-profile mentors who have signed on to help this summer include Bob Pattillo, founder of Gray Ghost Ventures; Dennis Whittle, CEO of GlobalGiving; Kjerstin Erickson, founder of FORGE; and David Bornstein, author of How to Change the World. In August, at the close of the institute,…