Does it do any good to "block" spam calls?

There are a couple issues with that service.

As regulated common carriers they’re obligated to transmit every call that enters their system. They’re not permitted to be gatekeepers. Except in the narrow cases where legislation has enlisted them in the fight against spam or terrorism or …

The second thing is how do they determine that a call is the kind of call a particular subscriber doesn’t want? It’s not like the calls contain some labeling. And just like spam email, there’s zero guarantee any label that might be applied is the truth.

Even if we instituted the death penalty for being a telemarketer, administrable on sight by any peace officer, all that would happen is the entire industry would shift offshore and use VOIP to get into the US.

I assumed most of these outfits are already offshore. Aren’t they mostly from India and Russia?

I set up a Google Voice number when I placed an ad to sell a car. There are lots of ways you can configure it. I set it up to forward to my cell phone, but first it requires the called to announce himself. Then they put the caller on hold while you listen to the announcement, and decide whether to take the call or let it go to voicemail. I think you can require announcements only when the caller is not in your phone book.