Per Don Y:
The best market driven solution is to charge a fee -- payable to the
recipient! -- to deliver the call. The recipient can then *waive*
that fee (press '*', etc.).

So, friends/folks you want to hear from you learn to press '*'
as a matter of common courtesy. If you forget, you promptly call them
back and "ding" yourself for a call -- which cancels out the call
for which you negligently billed them!

Telemarketers can factor that cost into the price of their wares.
Unwanted contacts would have to find some way to *induce* you to
waive the fee; if you simply hang up on them, they get dinged!

That is the most sensible-sounding solution I have heard so far - from
anybody, anywhere.

"Sounding" because I have no clue as to the technological or political
(think industry "lobbying") ins-and-outs of it.
--
Pete Cresswell