Kevin Smith explains (in great detail) the reasoning behind his selections in his rejected iTunes Celebrity Playlist.
Personally, I'm not a huge fan of these because I really couldn't care less what Rick Mercer is listening to, but sometime I'll take a look just for kicks. The only one I remember with any great detail was George Stroumboulopoulis' list and that's only because his list referenced one of my favourite songs (Hockey Skates by Kathleen Edwards).
I love Kevin Smith and I really didn't feel like reading through more than two of his song choice synopses.
While I'm totally stoked on the concept of celeb mixtapes, I don't need a fucking novel accompanying every song, so I can certainly understand why Apple rejected his excessively verbose ass.
I guess it's kinda like cultural anthropology - who knew I cared so little?