As someone else said, this looks like a solution in search of a problem. I get very little spam, and I can’t recall the last time the spam filter missed it. Hell, I get more physical junk mail than I do spam email, and that already costs money and is more annoying since I have to actually throw it out.
The real issue with spam isn’t the annoyance. Even when I used to get 15-20 a day, it took all of 5s to highlight and delete them. The problem is the resources that it uses and, thus, the cost to maintain that wasted bandwidth, and the extra storage space and processing, that is ultimately passed on to consumers. But it seems to me that most email services are taking active steps to correct the problem. I they detect high amounts of spam coming from certain IPs or networks, they take that into account in their filters and may even block them from entering their network. The better that can be done, the more expensive it becomes for the spammer to maintain a network that isn’t blacklisted on most or all of the most popular providers.
Worse, this seems to me like it would have a negative impact on my service. Of course I’d whitelist family and friends, but what about a new acquaintance, a friend changes email, I sign up for a new service. I’m not necessarily going to know all the email addresses I want to receive emails from. If I set that value too high, those people may not be willing to pay even believing that it’s quite likely I’ll retroactively give it back. If I set it too low, it will do little to discourage spamming, which would still be cheaper than junk mail or cold calling. In both cases, it puts a burden on me to maintain a list.
When it comes to mail filtering, we also have to consider the costs associated with incorrect classification. If I falsely identify spam as legitimate email, the cost is a second or two on the part of the user to realize it and delete it; it’s a very low cost. On the other hand, if I falsely identify legit email as spam, the cost is high. I could miss a bill, a letter from an old friend; in one case for me, I missed an important email from a girl I was dating and it made for an awkward conversation when she was under the impression I was aware of certain things and I wasn’t. The cost of a false positive is really high. Putting an actual monetary value on it just makes this whole situation worse.
If something like this were done, it would need to be highly intelligent sampling and the idea would be that the sender would be acknowledging that they don’t know me and I could get paid some small amount in exchange for viewing their email, set a threshold for how much I’m willing to be paid for the inconvenience, or straight up opt out. But that could be bad too since them being willing to pay for it may inadvertantly lend some credibility to a phishing attempt or a scam rather than just an ad.
So, no, this seems like a really bad idea to me. Spam isn’t a problem for most users, costs for spammers are increasing, even if it isn’t approaching being prohibitive. We’ll see better results as people are more educated in identifying spam and scams and we can instead make it prohibitively expensive by reducing the hits they get through that understanding, continuing to improve the existing filters, and encouraging people to use services with higher quality filters.