I decided to take gmail up on its Consider Including recs for an entire day; whenever gmail suggested I loop someone into an email thread I did it. I got a lot of "nathan, why the hell are you emailing me this?"s
Gmail uses the space for email-adding, "consider sending this email to x, y, and z as well", when I think it could be better used in subtraction.
Gmail says: "Don't send that to your boss." or,
"Don't send that picture to your friends, you're drunk." or,
"Don't send this break-up email to your boyfriend. I know you think he was lying but he wasn't, trust me, I can read his email. Additionally, I know that he is right now searching for local florist shops.. although he did misspell florist...."