So you know how when you get email you dont wish to receive, you click the spam button and it becomes blocked and can no longer solicit you. so why not push a button on the phone which will block the caller forever, you can push *89 to hide your number so why not *0 to block a caller. this way you get to choose who you block.
there are also sites that you can report the emails of spammers too, then that site compiles a list of IP addresses for spammers. what if you did the same with the callers, If I push *0 and the number is captured and goes to a list the FTC can access and investigate or not. When I build a forum site I can block IP address or emails, this could work the same for phone numbers.
The proof is in email spam, forum spam control, its easy