Ads can seem like the bane of the Internet. They take up real estate and slow Web pages while they load; at worst, they splash across the screen for interminable seconds, shout loudly and unexpectedly from an invisible corner, or surreptitiously infest the host computer with malware. Around two hundred million users worldwide have tools to block these ads and prevent them from loading, according to reports from the ad-blocking-circumvention startup PageFair.

Blocking ads, however, also keeps the Web sites you read from making money. And so, typically, sites try to earn back this business with appeals to visitors’ empathy: they ask you to please “white-list” the site and let it stay in business. Other sites go so far as to block their content entirely when they detect that an ad-blocking tool has been enabled. Sites including Wired, GQ, and Forbes have used one or more of these strategies to re-monetize readers who were blocking ads. (If you use an ad blocker while visiting newyorker.com, the slots usually filled by ads will contain messages encouraging you to subscribe, which my editors suggest you should do.) It should be noted that ad blockers do nothing to guard against—and perhaps even encourage—other forms of advertising, such as “sponsored content”—articles, photos, or videos that look similar to a given Web site’s content, but are commissioned by advertisers.

On Tuesday, Facebook, which has 1.7 billion users, announced that it’s taking this battle even further, in a way that only it can: with the latest version of its Web site, at least on desktop computers, Facebook cheekily defangs blockers entirely and serves its ads exactly where they would have been blocked.

The Times claims that Facebook’s site changes will make it much more difficult for ad-blocking tools to identify ads, and that re-blocking them after they’ve been re-served would require a resource-intensive analysis of the ads themselves. Wired noted that makers of the ad-blocking tools are already at work on a counterattack. (Facebook reported that it rolled out the changes on Tuesday, but at the time of this writing, Adblock Plus was still able to eliminate both sidebar ads and sponsored posts in the news feed. Facebook did not immediately respond to a request for comment on whether the new version of its site has fully rolled out yet.)

Facebook has a strong incentive to end ad blocking; it makes money on ad revenue. In a recent filing with the Securities and Exchange Commission, the company noted that ad blockers posed a significant threat to its business. Neutering the blockers would mean protecting its top line.

But ad-blocking software has been available for quite some time. The question remains: Why has the backlash cropped up now? To understand Facebook’s motivation, it helps to revisit Apple’s mobile ad blockers, which the company introduced last year. Apple’s mobile ad blockers, which have earned a lot of attention, work only on Safari’s mobile browser. But Apple’s entire mobile platform is built on closed-system apps, not Web-based sites. Ads served within these apps cannot be blocked by anything, not even Apple’s own ad blockers. So, by blocking Web-based ads, Apple’s move would, in theory, drive businesses away from the open mobile Web, where the future of advertising is shaky, and toward apps, where there are fewer business variables. It’s not a coincidence, either, that Apple makes money from apps through both sales and advertising, while it earns nothing from its mobile browser.

What was true of Apple then is even more true of Facebook now. Over the last few years, Facebook has seen rapid growth within its mobile app, where blockers don’t work and it can easily control the ad experience in the same way that Apple can control the app experience. This means that features of advertising that frustrate readers are gone (malware, surprise screen takeovers, unexpected noise), but some of it is still very much there (tracking, data collection).

Facebook has now shut down ad blockers on nearly all of its domain—first on mobile apps and now on desktops. (Blocking still works on the mobile Web.) This suggests to publishers that Facebook is a safe space where the business of content can be more effectively protected, on the condition that they submit to being Facebook’s vassals.

Individual publications, and even some publishers, lack the resources to mount an all-out arms race against ad blockers, not least because they’re unlikely to attract engineering talent when there are so many startups and established tech companies plying potential hires with equity—or at least free meals. Facebook’s ability to protect its revenue stream on the desktop version of its site only strengthens its position as a closed platform, a place where the user is powerless against its technical domination and will be gently served ads, whether they like it or not. This makes it an extremely safe bet as a place for brands to publish content. Instant Articles, while not yet a success, got a deluge of publishers on board because the model seemed straightforward, reliable, and immune to ad-block tampering. It helps that Facebook gives a good home to sponsored placements within its news feed. Publishers are safe there, sort of, for now, although they are also subject to Facebook’s semi-yearly whims, which vacillate between favoring the latest Facebook product (embedded links, videos, news, live streams) and the posts of users’ closest friends and family, as determined by its algorithms.

Facebook is still only one platform, but its cavalier attitude suggests the détente between ad blockers and Web properties is coming to an end.