"The internet is for porn" is a strange sort of conventional wisdom in that it's never quite been true. The internet has hosted porn for as long as it's hosted images, and it's made viewing porn both dramatically easier and infinitely more discreet. Yet the notion that the internet somehow orbits around porn is, and always has been, unlikely.

But that's about to change. The relocation of a massive portion of the internet into walled, squeaky-clean social networks, as well as the large-scale redirection of attention from desktop computers to smartphones and tablets with pointedly smut-free app stores, has left porn without a seat at the table. The new internet abhors porn; what's left of the old internet may finally be defined by it. The internet still isn't "for porn." But more and more, the web is.

Last week, Tumblr commenced a widely predicted crackdown on porn. Whether or not it's been deleting content en masse is still unclear, but seems increasingly likely. It has indisputably pushed porn out of view: For desktop users, porn is harder to find; for mobile users, the goal seems to be to make it impossible. The "porn" tag on the Tumblr site unfurls an infinite scroll of genitals, while the same tag in the Tumblr mobile app pulls up a blank page.

All social networks and apps must figure out how to make money from their users as a whole. Their owners' job is to figure out how to monetize the network, and Tumblr's new owner, Yahoo, is taking its job very seriously. Porn just gets in the way. In recent weeks, Google also made news by scrubbing early Glass apps of all adult content, and this weekend, the Daily Mail reported that the U.K. will institute an opt-out porn ban, requiring internet users to request special access to adult material.

These moves — a bold, business-driven repudiation of a large swaths of users that have enjoyed some of the most vibrant porn communities on the web; an overcautious response to guard an already-stigmatized product; a bizarre, old-school moral crusade — acknowledge the same converging trends.

"More often than not these are policy decisions," Stephen Yagielowicz, a senior editor at XBiz, an adult industry trade site, told BuzzFeed. "Censorship is a government act, but most often these are company policy issues. You can lean on boards of directors and they can lobby to change these companies' terms of service," he said.

"But, I mean, do you really want to have to go to the post office and fill out a form that shows you'd like them to be able to show porn at your home?"

The growth and exile of porn to the web has had some striking side effects for the tech world. Just as Google search has been reduced to a place where we ask the questions we don't want to share with the world, or even our friends, the browser, especially on mobile, has become a portal for the cast-off and incompatible: that is, content that's either incompatible with the major apps or social networks, or with the moral or business judgements of the companies that control the largest new internet ecosystems. (A less generous characterization: the browser as a gray market.)

For news, you open Facebook or Twitter or Flipboard. To talk to your friends, you text, use a messaging app, or send a Snapchat. To play, you open a game. This leaves very little for the plain browser, which, at launch, was the iPhone's primary portal to almost all content and communication: