OK... I'm the odd chick out... this doesn't bother me at all... I wouldn't even bat an eyelash over it... on the other hand, I DO realize it bothers many people and wouldn't do it myself...
I'm on my cell phone a lot, but do my best to be respectful, which means saying, "Hey let me call you right back OK?" at the appropriate times... I've never had a friend say, no you can't call back if I needed to drop the call to use the restroom, pay a bill etc.
I have to say, there have been several times when I should have dropped a call and didn't because the friend or family on the other end called because they were distraught over something...
There is a fine line between "hobby" and "mental illness".