This has definitely been an interesting case to watch... we signed up for the list.... I'll admit... we get hassled by telemarketers more than what I think could be considered as "normal" on our unlisted phone number. It's really frustrating.
I did do one thing that worked once for about a month... on our answering machine I made a message that said, "hello....? hello....? HELLO....? Oh, that's right, we're not home right now. Please leave a message and we'll call you if we feel like it." I think they got through the first 2 hellos and hung up every time. lol We finally took it off though because it kept pissing off friends/family - they kept getting fooled by the message.
Telemarketers.... something actually worse than those herbal viagra spammers!