Did you ever notice how it took you ten minutes to get back to work after that five minute phone call?  Or how answering that email reminded you of something else you had to do and you didn't get back to that spreadsheet until after lunch?

I've never really bought into multitasking for humans (as opposed to computers) and over the last couple years there has been a flood of research suggesting it's not only a bad idea but that it is basically not possible, a myth of sorts.  The NYtimes has a nice summary of current research and a reminder of why when we think we're actually doing 5 things at once we are actually getting very little done.