[dubya]

It's technically possible for sites to not serve content to those who use adblock. I remember arstechnica.com did this once to make a point. I guess if this was widespread, it would turn into an arms race though.

[throw_away]

I'm pretty sure that washingtonpost.com does this now. This URL, for example: http://www.washingtonpost.com/opinions/the-us-governments-ou... serves content if you have adblock plus turned off, but a registration page if you have it turned on.

[floomp]

I have ABP and could view the article for a few times, then I tried again and I got the registration page. Disabling ABP didn't change that. I have a feeling it's based on how many times you've viewed their site rather than ad blockers.