So many unexplored business opportunities, so little time. : "Great execution is at least 10 times more important and a 100 times harder than a good idea," Y Combinator President Sam Altman has said. Apparently he - and the famed incubator he leads - really believes it. Recently ex-entrepreneur turned Y Combinator software developer Kyle Corbitt reached out to program alums and staff members asking them to publicly share their best startup ideas that they don't have the bandwidth to build. He then published them on the Y Combinator blog.