We have a similar setup in the UK but it's never had any big advertising apart from the telephone directories and mentions in the newspaper etc.

My gran wasn't on it but after she was complaining about getting several phone calls every evening I signed her up to it and she said she will maybe get one call every other weekend and as soon as she mentions "telephone preferen...." they hang straight up!

I keep telling her to get the name of the company first so that she can report them but no luck.

They do a junk mail version too (Mailing Preference Service) and that cut back the crap she gets posted a huge amount. It's administered by the UK DMA but seems to be very reputable.

Gareth