For a while....quite a bit of embarrassment that I wasn't even aware I had on my iPod. When my oldest was 12-13...I gave her an iTunes monthly allowance for Christmas. Fast forward a couple of years... Apple gave people the option of paying a minimal per-song fee to d/l DRM-less higher quality versions of past purchases. I jumped on that.
Unbeknownst to me, everything she had purchased came along for the ride. It certainly made for some puzzling shuffles... Where the hell did THAT come from??