I was at a comics store (Chicago Comics) yesterday when a pair of startup guys came in to pitch what sounded like a loyalty program. (I didn't catch the name, but they said something about users getting points called "pixels", if anybody recognizes it.) The owner politely but firmly brushed them off saying that he'd heard from a dozen similar startups and he was just going to wait a few years to see which survived and became worthwhile.

So there's a fourth reason: there's enough of these startups that small business owners are sick of you.