The Internet is now eating its own.

News portals like AOL, Yahoo! and MSN, which helped devastate newspapers, magazines and local TV over the past decade, are themselves being damaged by social networks, notably Facebook.

Facebook, the latest Web sensation, is becoming the preferred news source of tens of millions of Internet users. Facebookers can keep up with just about anything without ever leaving the site. Their friends provide a neverending news feed, posting endless links and news items.

And just as the news portals grew fat by cannibalizing content from the legacy media, Facebook links are as likely as not to come from the portals (which probably swiped them from a newspaper).

But it’s the intensity of Facebook use that really sets it apart. The average Facebook user views about 27 pages on each visit, according to the Web-tracking service Compete.com. That’s several multiples better than the major news portals. Yahoo! users typically view about eight pages per visit, while AOL users view about seven pages and MSN users about five.

Time spent on Facebook continues to grow at the expense of news portals (and other websites). The three top news portals saw their average time per visit drop by about 22 percent over the last year. Meanwhile, time spent on the average Facebook visit was up almost 50 percent, to nearly 23 minutes.

Journalist Dylan Stableford suggests that the way out of the portal dilemma is with original content, a path several of the portals are aggressively pursuing. Create worthwhile original content, the idea goes, and users will wind up spending more time on your portal.

That’s an idea well worth pursuing, I think – content is king on the Web, and eyeballs will go where content can be found.

But I think the content-creation strategy is better suited to tightly defined niches, a subject I’ve written about for MinnPost in the past.  If portals try to be everything to everybody, they risk the same fate as that other great generalist, the newspaper.

And I have no doubt that two years from now, I’ll be writing an item about the new service that’s bleeding Facebook dry.