The whole situation bears an interesting contrast to the battles over anonymity on the Internet, where the telephone industry is trying to preserve the ability of their customers (telemarketers) to avoid detection.
It was clear that most of the telephone industry really hates phone spammers. An AT&T guy was saying that evil robocall outfits often forge the numbers of their existing customers, causing AT&T no end of headaches. Plus they get a ton of complaints from call receivers. I am sure that the major carriers would shut down phone spammers in a heartbeat if it were easy.
Looks like the FTC now has the videos from the summit up on the web:
http://www.ftc.gov/bcp/workshops/robocalls/
Anybody seriously interested in the problem should check out the videos. There's a lot of good stuff in there about the technical issues. And there are some interesting technical solutions as well.
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.
But the infrastructure is the real problem. So many switches around the country are so old that hops through the network are very difficult to track and make any innovative technology solution hard to implement fully.
Caller ID can still be forged
It's quite popular with the internet telephony providers to relax the rules a bit. Basically some allow you to check the "I promise not to break the law, believe the data I send" and will accept any caller id you want. Since there's no way for one telco to verify other telco's source numbers, everyone else has to believe your caller id too.
This wikipedia article has a reasonable summary: http://en.wikipedia.org/wiki/Caller_ID_spoofing
The easiest way to get into spoofing CallerID is by using a SIP-driven POTS gateway (very common 6 years ago, telecom moves very slowly, so I suspect they are still easy to find today). Some providers will validate the number you want to announce, and prevent you from announcing a number that they don't think you should be using. Others don't care at all. There are a lot of different telecom service providers, so finding one with lax policies isn't hard.
Almost anyone who is actually operating a phone card business has all the equipment needed to do this, for example. Phone cards are incredibly competitive, so if you head over to your local telecom hotel you won't have much trouble finding people willing to take your money in exchange for steady business.
The next time you are in a data center, take some time to talk to the people messing with the funky gear that doesn't look like any firewall or router you've ever seen.
There would have to be a global opt-in system allowing to verify those cases. And it would be as effective as the DNS records for verifying sender domains - you probably want to assign it a score, rather than reject right away.