As the social networking era entered the mainstream, Rupert Murdoch paid $580 million for one of the Web's hottest properties, MySpace. The chief executive of the company that Mr. Murdoch outbid, Viacom, was fired after his boss complained that losing was a "humiliating experience."

That was five years ago. A few weeks ago, MySpace fired half its staff of 1,100.

MySpace's decline again shows the fragility of social media, where fickle consumers make services like Friendster suddenly seem indispensable, but fade just as quickly. According to comScore, MySpace reported 54.4 million users at the end of November, 9 million less than the previous year.

"MySpace was like a big party, and then the party moved on," Michael J. Wolf, the former president of Viacom's MTV Networks and managing partner a media consulting firm, told The Times. "Facebook has become much more of a utility and communications vehicle."

The detritus of the Internet includes many once well-known names. Netscape. Infoseek. Alta Vista. CompuServe. Excite@Home. Webvan. Boo.com. Could Facebook, which now gets more hits than Google, some day join them? What passes for posterity in the Internet age? What will be left once the digital dust settles?

Goldman Sachs invested $450 million in Facebook at the beginning of the month, which puts the value of the company at $50 billion. But before Goldman bought that stake, a powerful investment group within the firm turned down the chance to buy in, The Times reported. One reason Richard Friedman, a longtime partner who manages the group, might have avoided Facebook was that his fund was hurt a decade ago after loading up on technology and telecom favorites during the dot-com bubble, according to The Times. One of the unit's funds, which raised $2.8 billion in 1998, invested about 70 percent of its portfolio in Internet companies, The Times reported.

The dot-com bubble became the dot bomb in 2001. One of the Goldman's investments, Webvan, collapsed. It had been backed by Goldman's chief executive at the time, Henry M. Paulson Jr., the former United States Treasury secretary. Mr. Friedman, it seems, learned an important lesson.

Webvan.com, now owned by Amazon, lives on. One of the eerie realities of the social networking age is that digital imprints last long after users have departed the physical world. Of the more than 500 million Facebook members, some 375,000 of them die annually in the United States, The Times reported.

The architecture of the Web has speeded up one of capitalism's most ruthless aspects, creative destruction, where companies are cast aside like old cellphones. But it is more forgiving when it comes to personal legacies.

Facebook posts, Twitter feeds and YouTube videos will survive after the body is gone. It turns out that cyberspace may be more generous to individuals than companies that have capitalized on its technical capabilities.

Paul Kimball, a filmmaker who lives in Nova Scotia, has developed many close friendships online and even collaborated on a play with one Facebook friend who has since died. He told The Times that he was "still having this conversation" with his late friend by posting a link to one of his dead friend's Facebook posts and having those in his online circle react to it.

"We're entering a world where we can all leave as much of a legacy as George Bush or Bill Clinton. Maybe that's the ultimate democratization," Mr. Kimball said. "It gives all of us a chance at immortality."

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