This is terrible. I had no idea this had happened till now. I am so sorry. If I had known we'd accidentally sent these people an invitation to interview, we would have just gone ahead and interviewed them.
As far as I am concerned, this is the worst mistake YC has ever made, and we will try never to let this happen again.
Its easy to create perceptions of yourself that are simply not true. I was one of the people who got that mail. I really thought about shooting an upset sounding email to Paul. But thought the better of it -- amazing that every other person on that list did the same. Only when I met the YCombinators on the interviews to a subsequent cycle did I figure that they were nice people (inspite of not making it). Absolutely no hard feelings, though. Looking back, I simply was not prepared enough to do a startup. I eventually got around to realizing that I did not need money to built a product -- just a committed co-founder -- and so thats what I did. Yesterday's rejection did not sting at all.