I think Rapportive is really cool and useful for a few of the emails I get but I'd like to have it off by default, or at least be able to turn it off for specific contacts.

The ability to turn it off entirely on my address when it's enabled on my domain would be an acceptable alternative.

(My work enabled Rapportive for the entire domain, so I can't turn it off for my work gmail. About 90% of my emails are to a group of 5-10 engineers that I work closely with and seeing the same information on the bottom of every email gets a little old.)