Social Norm – E-mail, Voicemail, SMS

Are there social norms around responsiveness to communications?  I was reading this quote and realized that I am obviously not fitting the norm.

“The social norm is that you should respond [to e-mail] within a couple of hours, if not immediately,” said David E. Meyer, a professor of psychology at the University of Michigan. “If you don’t, it is assumed you are out to lunch mentally, out of it socially, or don’t like the person who sent the e-mail.” (source)

There are many days when between travel, client meetings, conference calls, hundreds of e-mails, and trying to read all the things I get that I barely respond to anything but critical e-mails.  Add a few conferences or a day off here and there, and it’s literally impossible to keep up.  So, if the expectation is immediate due to blackberry’s and other smart phones, I guess I’m in trouble.