When I watch those commercials, I always assumed the scam was that they were sending you a "free CD", but charging a good price for it with their "shipping and handling charge".
Agree. I've seen those ads more times than I can count, and never thought they'd be sending 30 CDs, and billing me if I didn't return 29 of them.
The ads clearly lead you to think they'll send 1 CD, possibly charging S&H, and it will prove its merits thereby leading you to purchase further products. I believe he even says as much.
I wasn't nearly cynical enough it seems.