I think it's a little optimistic to expect any rev-share with recipients, but creating a better economy on the
sending side of mass electronic solicitations is a good idea. The only reason our postal mailboxes aren't dumpster-sized and full of junk mail every single day is the cost of planning, producing, and mailing the physical piece of mail. Email is a shit show because the costs of mailing are near zero, and the cost of producing is decoupled from the number of recipients.
If there were a hard cost per recipient, the ROI of email campaigns would change significantly. This change would be positive for users. The question is whether or not senders would bear the burden, or if they would flow to "less legitimate" means of reaching recipients on Facebook. It may be that senders would more willingly accept lower actual reach rather than pay the additional cost.