This is the only realistic practical solution we have so far. The other ideas here cannot be done because incentives are not aligned properly. Fining telcos? With the FCC and most lawmakers in the pockets of telcos, this is not going to happen. Cryptographically secure CallerID? Who would pay for this? Telcos cracking down on robocallers themselves? No chance, since they make money from robocalling.

It's like asking the post office to solve junk mail. Where's the incentive?