For Yom Kippur 2013 (ha--I mean, 5774), I decided to go off-line for 24 hours--from 8pm Friday (which is pretty much sunset here) to 8pm Saturday. Here were my ad-hoc rules: I could use my computer and my phone and my iPad--it wasn't an electronic fast; but I couldn't use FaceBook, Twitter, email, blog, forums, RSS feed, etc. Basically, I had to stay away from everything digitally social; everything where part of the protocol is interacting with people / waiting for people to interact with.
My logic: Is there anything both more addictive and less satisfying than refreshing to see if someone has responded to an email or favorited your tweet?
Now, as an indicator of how deeply ingrained this sort of stuff is in my mind, I had a dream on Friday night about getting really interesting email. Let's do the math on that: I stopped checking my email at 8; and sometime after I went to bed at 11, I had a dream about email. Then, that Saturday morning--after making brown sugar-bacon waffles--I was making jokes with my girlfriend about how it would be fine for her to check my email.
Then, while I was doing other things during the day, I noticed how often my hands would just habitually go to click over to my browser. On normal days, I will check my email in between sentences that I'm writing, which doesn't help the writing much and doesn't make interesting email appear. (To be clear, I prevented myself from doing that today by closing my browser and turning off most wi-fi capabilities. No accidental digital eating for me today.)
And it was also hard, at first, to think about the news or jokes or opportunities to tell jokes I was missing; though later, I semi-successfully adopted the attitude that there will always be more news and more jokes-portunities later.
Overall, I would recommend a social-digital fast and might try to institute smaller fasts throughout my days. (Though that's rather like calling the time in between breakfast and lunch a fast.)