How random is the iPod's "Shuffle" feature?

My first iPod loved Steely Dan. So do I. But not as much as my iPod did. By 2003, among the 3,000 or so songs in my iTunes library, I had about 50 Steely Dan tracks. Yet every time I shuffled my music collection "randomly" to mix the tunes, it seemed that the Dan was weirdly over-represented. Only two or three songs after Rikki Don't Lose That Number, I'd hear Kid Charlemagne. Then, 20 minutes later, there would be Pretzel Logic. Where was the logic in this? I didn't keep track of every song that played every time I shuffled my tunes, but after a while I would keep a sharp ear out for what I came to call the LTBSD (Length of Time Before Steely Dan) Factor. The LTBSD Factor was always perplexingly short.

Oh No, Not Steely Dan Again (Steven Levy, The Guardian, October 7, 2006)

I have quite a lot of Steely Dan on my 8G iPod Nano, too, but *my* iPod's favorite artist seems to be Louis Armstrong, so I've got the MTBS (Mean Time Between Satchmo) effect, even though the number of Armstrong tracks is not quite as high as some other artists (I've got complete Charlie Parker and Bud Powell box sets on there, for cryin' out loud.)