I was just thinking about Turntable a few days ago. I never really got into it. I don't doubt that industry costs weren't a major factor, but I also wonder if retention was an issue. It seemed a nifty idea, but I don't personally know any long-time users.
I think their biggest problem was they focussed way too much on headbobbing avatars and not enough on features and stability. Every experience I had with turntable was excruciatingly broken and the cpu-sucking bullshit flash animation didn't help.