Well, I know for myself: email is enough of a distraction without adding twitter to it. Rapportive provides a useful service by providing me more information about my contacts. By adding the ability to reply to twitter, though, it becomes more than service providing information; It ends up becoming another possible distraction. No, I don't have ADHD. I just have little self control when it comes to things that pull me out of writing. My brain resists work.

Also, of course, there's the fear of inevitable feature bloat. A service that works well at one thing should continue improving in that area without adding unnecessary features.

Way too much sensitive data in my gmail account that I don't want broadcast to the world via twitter. It doesn't matter what kind of controls are in place, I'm not taking the risk that all of my online shopping, password resets, private email, etc. gets accidentally tweeted.

I can understand your concern, but the only time we tweet anything is when you click a button asking us to do so; it's very hard to imagine how we might introduce a bug which would accidentally tweet the contents of your emails.

I think his concern is not about a bug tweeting private contents, but any kind of exploitable bug that might give access to his account in any way, form or duration.

There's probably no way around this, since any addition is a possible attack vector.

That guy must be really, really, mad. Who would not like "allow access to data on mail.google.com"?