I wouldn't call it blackmailing. It's flat out extortion; they build a script that blocks ads for specific domains then tell the owners they can pay to have it removed.
To be fair: Adblock Plus does not simply block ads on some specific domains, EasyList and other filter lists are pretty extensive. I do not like the business model either but how else could they make the necessary profits?
Adblock Plus (and similar add-ons) were not created because of such a business model but because of annoying and sometimes even dangerous ads.
I don't think Adblock Plus is worthy of revenue - their "business model" is to squash other companies revenue then make them pay to get it back. Sure, they block a lot of super annoying and even some potentially dangerous ads, but most of the time they're blocking harmless banner ads on small sites that need the revenue to stay online. This obviously isn't just Adblock (Plus)'s problem - there's always going to be someone trying to remove ads from websites, I just wish those creating the scripts would apply their talents elsewhere.
