How is this blackmailing?
Strictly speaking, blackmailing involves using knowledge of someone else's transgressions against them (e.g. "Pay me $1,000 if you don't want me to show your wife these pictures of you having an affair.") I don't see anything close to that happening here. I mean, AdBlock isn't saying "Pay us to serve your shitty ad". They're saying "Pay us to ensure that your ad meets the high standards of our users, in which case we'll see that it's delivered."
Big, big difference.
Like a lot of people, I'm not adverse to ad-supoorted content in principle. And I recognize that smaller sites can't have dedicated ad-sales units, and need to rely on ad networks to connect their audiences with advertisers. Unfortunately, this means giving up a lot of quality control, and that ends up producing a crappy experience for readers - who then resort to AdBlock, which degrades the value of the Internet as an ad platform for non-horrible advertisers. This downward spiral is part of the reason that print outlets can charge so much more for the same reach online.
AdBlock Plus seems to fix all three problems at once. By applying some reasonable criteria as to what is an isn't a horrible ad (to say nothing of crap infected with malware), it makes it easy for me to filter out the worst ad networks, and only engage with the ones that enforce some basic standards. Assuming that ABP gets widely adopted, they provide a great way to drive the worst offenders out of business, leading to a world where sites and advertisers gravitate to the networks that offer the highest penetration.
In essence, ABP is a buyer's agent, with the buyer being the reader and the currency being their attention. And thanks to the efficiency of my agent, I don't have to waste my time rejecting the crappiest bids. At the same time, I can participate in the ad-supported model (which I frankly prefer to paying cash). With less crap in the mix, this model actually becomes increasingly beneficial to sites as online ad-rates increase. Far from something noxious like blackmailing, ABP seems like a fundamentally civilizing influence.
The gold standard in all of this is Vogue, and specifically, their September Issue, which would actually be worth less is the absence of all the ads. And yes, you better believe those ads are heavily vetted by the magazine. In a world with competing blockers / coaches, the agent who gets closest to this mark wins.