[jerf]

"I doubt there's a perfect balance, but either extreme come with too many problems."

In principle, "pay me a small fee if you're not on my list, if I put you on my list now it's free" would work well (optionally refund someone who contacts you out of the blue that you approve of), but there's a lot of both engineering and social details between where we are now and such a system.

It doesn't take much cost friction to deter mass spamming. I don't think much problem would be left behind from the handful of overconfident spammers who think that they can bust the odds and it's worth 25 cents a message or something.

[dalbasal]

This is one of those ideas that appeals to economists and nerds, but rarely works out irl.

Artificially or intentionally aligning interests tends to be a "genie, make me a sandwich^" problem. There are lots of places where "reversing the charges," seems good in theory... but it never happens.

Anyway, linkedin have something like this. In practice, it feels like a better quality of spam, rather than a solution to spam.

^Poof. you are now a sandwich.

[shuntress]

Sounds like a good idea on which to base an ISP startup.

"Anyone not on your contact list will take $1 off your monthly bill for each phone call, SMS, or eMail they send to you (through our phone line & email servers)"

[biot]

This is nearly a few decades old (2004): https://craphound.com/spamsolutions.txt