Today, I tried to get one to leave me alone. I got a recorded call from "Mike's Carpet Cleaning", and hit the "talk to a person" button. After some very hard-to-hear greetings, I said I wanted to be put on their "do not call" list. I was immediately hung up on. I hit the internet, hoping to give them some bad press. It turns out, there appears to be no such business. Other people have been called by them and gotten a variety of questionable-sounding information about a business that appears not to exist (there's a Mike's Carpet Cleaning in Walnut Creek, possibly defunct -- this caller is not that business). I immediately thought, "oh, like a Phishing scheme, but on the phone, you'd give them a credit card number for a deposit." My very perceptive wife pointed out that actually, a carpet-cleaning business would be an excellent front organization for burglars.
So if you're on the "Do Not Call" registry and still getting calls from businesses, don't just avoid paying them because they're being inconsiderate. Do it because there's an excellent chance that they're completely fraudulent, and you're likely to be (literally) robbed.
Somebody out there is either attempting to run a phishing/burglary business by being a telemarketer (a fine vision of Hell), or is hired as a telemarketer, at minimum wage, *by* a phisher/burglar, which would indicate that they'd make better money by turning their employer over to CrimeStoppers.
On a related note, I'm happy that the internet now allows looking up various caller-ID'd return phone numbers to see who has received spammy or fraudulent calls from them. I don't do it routinely, but it's exactly the kind of thing I think the internet should be good for.