You are right that "pay to send" solves the spam problem. But gmail filters spam so well that this is already a solved problem. Additionally, the sidebar ads

You are right that "pay to send" solves the spam problem. But gmail filters spam so well that this is already a solved problem. Additionally, the sidebar ads in google or facebook are auctioned off to the highest bidder. So users are already receiving improved targeting based on pay-to-send. The only problem I see this solving for users, is that they collect the money instead of facebook or google. That is very little money on a per-user basis. So it's not solving a meaningful problem. I agree that there is huge potential in "pay-to-send." But this marketing appears to be off-the-mark.