And each of them tell all their friends that you are an a-hole, then when every potential hire in Cambridge/ NYC/ Stanford etc has heard that XYZ software are a-holes you are going to have one hell of a job hiring.
Plus, if the 1 developer you DO hire continuously tells people it's a great company working on cool stuff, that would outweigh the negative comments from the other 99.
If you are a small startup in a high tech hub trying to attract people, and especially if you are in a market where the programers you reject might be future customers then you're risk is different.
Companies often forget that the people they reject don't disappear. It used to be a big thing in merchant banks in the last boom to really grind and humiliate candidates - you aren't smart enough to work here etc. What they forgot is that those people went to work for companies that might need a merchant bank and that the victim is suddenly the customer.