Wouldn't it be fantastic to have LIKE and RECEIVED buttons to respond to an email?
They'd be perfect for those times when an auto-response seems too impersonal, and a full email is either unnecessary or too time-consuming.
Of course, I'm not the first to think about this. The concept is controversial one, as noted in this GMail Help forum.
Okay, so I concede that these buttons would be too invasive for personal emails, but they would be very handy for doing business, I think. I would definitely use them!
Google, are you listening?