I've heard lots of people complaining how email, blogging, Facebook, and other necessary evils are keeping them from getting their writing done. This isn't about the Internet. It's about your self-discipline.
Shut off noise distractions. You know, the little nifty sounds that your iphone or Droid might use to alert you that you've just received a new email, or FB or Twitter comment. Same thing with your computer. Turn off the sound alerts. They only serve as distractions while you're trying to write.