Saw them @ startup school as well, and I could see it being useful. I'm not sure what the business model is, I wouldn't have called it "stupid"
I imagine they put the IP warning up in response to the techcrunch press. The real solution would be a message when someone picks up telling them to "Press 1 to stop this service from calling you in the next hour. Press 2 disable it permanently"
At risk of starting a lot of crank calling:
http://phonemyphone.com/