In reply to Flinticus:
A friend who'd recently got into dance music bought an album by a cool artist of the day, I forget which one now. The gatefold sleeve had three 12" enclosed, so she treated it as an album and played it at 33. She got really into it and played it regularly. One day her cool mate came round, who was supposedly well versed in current music. My friend gets out her cool album and plays it. Cool mate checks the cover, nods along and remarks on my friends good taste. Months later my friend hears cool album played at the correct speed and asks what it is. "But I've got his album, and it doesn't sound anything like this" she says. Eventually it dawns on her what's happened.