Hacker News has a feature called "noprocrast". Here's how they explain it in the FAQ:
In my profile, what is noprocrast?
It's a way to help you prevent yourself from spending too much time on HN. If you turn it on you'll only be allowed to visit the site for maxvisit minutes at a time, with gaps of minaway minutes in between. The defaults are 20 and 180, which would let you view the site for 20 minutes at a time, and then not allow you back in for 3 hours.
If you try to use HN when you precommitted to not using it, you'll get the following message from them:
Get back to work!
Sorry, you can't see this page. Based on the anti-procrastination parameters you set in your profile, you'll be able to use the site again in 43 minutes.
I was thinking that something like this would be awesome for LessWrong. Personally, I have a rather large problem browsing the web - which includes browsing LessWrong - when I should be doing other things. After reading Digital Minimalism, I get the impression that such struggles are moreso the norm than the exception.