The idea of a CLI reputation service comes to mind. You'd have to have something to make sure that submissions tp the service are sufficiently difficult for voice spammers but easy for legitimate originators. However such a thing requires traction to work (just like DNSSEC, SPF and DomainKeys) so it might be a long wait...

On 15/05/13 17:24, I put the Who? in Mishehu wrote:
There are already sites like this up, but they don't act as a blacklist.  More so they're forums where people talk about what type of calls they received from a given phone number.

-Yossi