This was a really common tactic at Microsoft back in the 90s, which is probably why Joel is familiar with it. It worked on me--I took an internship with MSFT instead of Apple, because Microsoft gave me under a week to respond, and the recruiting manager at Apple was on a week's vacation.
Microsoft is still very notorious for this. It's a shame, because out of the top five (Amazon, Apple, Facebook, Google, and Microsoft), I felt that they otherwise have the most pleasant and effective recruitment policies (Google being the polar opposite here).
