I've read a number of the "showed up on the first day of work, went to lunch and never came back" postings and kept asking "do people really do that?" Apparently, the answer is "yes," because we had one this week.
Without going into detail, our hiring process is a mess. To circumvent some of the issues, our CEO(!) hired a developer on a contract-to-hire basis, with a 2 month contract. A pretty good idea since we haven't had the opportunity to fully vet the candidates; there's little risk for either party. The developer showed up on the first day and left after 4 hours, telling the contracting company that it "wasn't a good fit." There's some speculation that the developer had a better offer, but my guess is that they were put off by the offices -- the bulk of the team are in some temporary space and it isn't nearly as elegant as other places in the Silicon Valley (and this developer had been at one of the ritziest.) Personally, I would have worked through the contract and then left.
The developer's name is going into my "bad apples" file.