You can see it everywhere. For example, on Forbes.com, but also on many other small, as well as major online magazines.They do not want to let you be on their website if you are using AdBlock. The reasoning behind is that you are consuming their content for free because they are funding it through ads and that’s not right. And so they do not let you in on their website.
I’ve had a similar approach though. I take a lot of pictures, and I give them away for free: online, in full resolution and without any conditions like signing up for newsletters or registering to the website; even though the majority of picjumbo’s income is from ads.