Before I left, I asked if I could form a small team and take part in a 2-3 month project. They had initially planned on a team of 20, but I felt that small teams, left alone and working in small timeboxes, could perform just as well.
Of course, we performed much better than the larger team, but the reason I tell the story is this: for purposes of my own experiment, I stopped reading emails.
The customer loved what we were doing, and expanded the project some. I think it lasted 5 or 6 months total. During that entire time I never turned on my email program.
I finally left the job. God knows how many thousands of emails built up in my inbox. But it was never a problem.
It was also one of the nicer experiences I've had in technology. The team just called each other or walked to each other's cube and chatted when we needed to talk, and the day was nicely free of useless distractions.
Why? I think the problem with email (and IM and FB now) is that everything has the same interruption power. The email from HR with the monthly newsletter has the same ability to disrupt your day as the email from your accountant telling you some terribly important financial news. All of it involves you switching contexts, scanning the subject line, and then deciding to deep-dive on the material or not. Hell, by the time you've switched context, you might as well read the article: your concentration is shot. Ten seconds of scanning an email header might take five or ten minutes to recover from. It's not a good trade-off. Of course, there's also the fact that people email/IM/FB others simply because they can, whether they have anything of import to say or not. You'd think twice if you had to walk over to somebody's cube to show them a picture of a cat, but you wouldn't blink an eye to post an article with the same content to 100 people on FB.