We definitely would love to have a solution to where we could guarantee that no illegal calls are being made (Recent Blog Post: http://blog.call-em-all.com/3-reasons-we-are-excited-about-f...). We have our own internal checks but something which can be implemented on a higher level would be great for us.
The reality is that with the mix of old tech and new tech (read VOIP), tracking who is really making the call is very hard right now (timely and costly). Scammers knowingly break the law and unfortunately, a list of people saying don't call isn't going to stop them from scamming.