Yeah, I know, free is always supposed to be better. But the problem of spam is caused entirely by its being free. Here is an example:
According to the indictments, between 2009 and 2012 Nguyen and Vu hacked at least eight email service providers -- the companies that collect your data under slightly more legitimate circumstances -- to steal marketing data containing over a billion email addresses. After that, they worked with Da Silva to profit from the addresses by sending spam with affiliate links for a company he controlled, Marketbay.com.
At least according to the DoJ, all of that work netted around $2 million in affiliate marketing fees.
We don't have any idea how many emails they sent to each of these billion addresses. But let's say they sent 10 spams to each (probably a low guess). That is 10 billion spam emails for a net revenue of $2 million, or around $.0002 per email sent in revenue.
Long ago I proposed that (and I am not sure how to do this technically) emails should cost $0.001, or a tenth of a cent, to send. For you and I, say if we sent 200 emails a day (an email copied to 5 people would be 5 emails for this purpose) it would cost us 20 cents a day or about $75 a year, not much more than we pay for security software and updates. But if you could make it work, spam would be reduced drastically. No way there is any profit in sending an email for $.001 for an expected return of $.0002.
I have no idea in the current structure of the Internet how one would even do this. The charge would have to come from the receiving end, somehow refusing to deliver it if it does not get payment information. However, anyone who is going to steal a billion email addresses could likely hack the payment system.
I was going to call this tragedy of the commons, but that is not really quite right. Tragedy of the commons is sort of related to free public resources, but is more of an issue of lack of property rights than of the zero price.