This is repulsive as a concept and a business.

The internet is already polluted with ads. Why bring them to personal email communications?

Why can't we have any space that's free from commercial manipulation?

If this becomes widespread, I'm going to write a Gmail plugin to detect it and send it to spam, where it belongs.

If you're requesting someone's attention with an email, at least have the decency and respect not to monetize the attention they're giving you.