Apparently
The shuffle function in iTunes used to be entirely random (well, as random as computers can make it)

However your brain is programmed to look for patterns and coincidences; in a random sequence there's still a chance of four Monster Magnet songs coming up, but your brain will flag it up and you'll think 'that's not random!'

They apparently had to modify the code to make the Shuffle function LESS random, so it didn't play songs by the same artist in a row, which makes it appear MORE random to your brain. Weird eh? There's options in iTunes now to determine the 'level of randomness' or something.

I don't know which of the Shuffle algorithms your iPod will be using...
(Son of Sam-i-am We're all as mad as hatters here, Tue 23 Dec 2008, 11:58, Reply)