They aren't buying iMacs, either. I work at one of the largest unis in the US and everything is dell optiplex from the libraries, to the lecture halls, to the research labs, and the hospitals. The only iMacs I've seen are requested specifically by faculty for their office, or are 10 years old in some windowless back room hooked up to a random microscope running snow leopard. That being said, I've never set foot near any art buildings so I don't know what happens in there regarding their machines.

Two colleges instead of one don't make it less anecdotal...

Are many colleges buying computers at all? My university CS and engineering schools both just required that students supply their own computer that was sufficient for the coursework.

Yes. There are departments outside of the CS and engineering schools and also colleges that cater to lower income students that don't require you to purchase a computer.