So I assume this is self-evident to anyone who routinely avails themeselves of the Internets, which is, by definition, pretty much everyone reading this, but: One of the reasons the Net is so lethal to productivity seems to be the way it facilitates modular procrastination. That is, it used to be that if you were in the midst of getting something medium-sized done, most of the available modes of procrastination involved a fairly clear up-front time commitment. If you felt the urge to read a magazine or book, or do some cleaning, or call a friend, or watch a TV show or movie, or whatever, you were clearly allocating a good half-hour plus to that, and could weigh the extent of its interference with your task accordingly.
The Net, however, offers half a million ways to procrastinate that, at each decision point, you can tell yourself “will just take a couple minutes.” Oh, I’m just going to check my email, refresh my RSS feed, IM that friend I haven’t talked to in a while who just signed on, see what’s up on Facebook, watch the new Strong Bad Email, take a gander at this funny YouTube link, et multa cetera. It adds up to just as much time spent dicking around, but in increments that seem individually negligible. It’s presumably the same trouble many folk have quitting smoking: This one additional cigarette won’t make a difference, but they’re all “this one” cigarette.