Erasing the Web's memory bodes ill for Facebook and Twitter.

We saw the end coming for months, but it still brought a bittersweet torrent of nostalgia. GeoCities—that abject wasteland of blinking gifs, strident midi files, neglected guestbooks, and never-built pages “under construction”—died last week. And only after it vanished was it considered worthy of remembrance.

"G'bye, Geocities :')" ... “So, we’ve come to the end of the road.” ... “A part of my childhood and life. Big landmark for me.” ... “**sniff, sniff** what fond memories of learning HTML back in the day” ... “Way to kill early Internet history.”

Thus the new Web laments the old. Yahoo (YHOO) has unceremoniously kicked GeoCities out of its frayed and grayed empire, a fairly straightforward deletion from its servers that also tossed countless moments of intimate revelation and ordinary madness—all of which somehow seemed worth recording a decade ago—into the digital woodchipper. Like the obit of a friend forgotten for years, the news seemed to strike many old-timers as slightly tragic and weirdly significant in ways that future generations would never understand. Throughout the eulogies, there runs a string of complacency that the Web is nevertheless a much better place now.

But is it? Just as GeoCities heralded the Web of 2009—a fertile, expanding canvas where we can scrawl our personal graffiti—the death of GeoCities augurs the fate of the Web we are collectively building today. Think your delightfully spontaneous tweets and updates won’t, given a decade, congeal into the same boorish clutter that was the bulk of GeoCities? Think the profit-minded corporation hosting terabytes of communal verbiage won’t pull the plug like Yahoo did this week? Think again.

Ten years from today, the Web, now experiencing a period of unprecedented growth and mainstreaming, will become that much harder and more expensive to preserve. Google reckons the searchable Web grew from 26 million pages in 1998 to more than 1 trillion pages 10 years later. This year, Facebook alone may account for one-quarter of all page views. Who’s going to archive all that?

Probably not corporations. For Yahoo, the business case to shut down GeoCities couldn’t have centered on cost-cutting. GeoCities’ 23 million pages filled up an estimated 10 terabytes of data. Not long ago, that was a lot, but consider: Storing 10 terabytes on Amazon’s S3 pricing would cost about $1,500 a month, less than a studio apartment in many cities. No, Yahoo just couldn’t stand having idle Web pages that weren’t bringing in revenue. Besides, having a domain that had become a garish joke wasn’t exactly keeping its brand fresh.