Is Martin Eisenstadt, the neo-conservative think-tanker who claimed to have spread a rumor that Sarah Palin didn't know Africa was a continent, real? Perhaps not, but then again, how do we know if the New York Times, the august journal which exposed him, is real, either? Eisenstadt, a Times article reports, is actually Eitan Gorlin, an actor playing the part of a neoconservative think-tanker. Gorlin's response on the Eisenstadt Group website he created as part of the hoax: How do we know this is the real New York Times? Times writer Richard Perez-Peña pokes at the incident's surrealism, quizzing his sources on how they, too, can prove they're not part of the hoax. But our tenuous grasp of reality is far worse than his gibes suggest.In an age of Photoshop, Iran can have as many missiles as it wants; headlines can be faked; and bodies altered beyond any relationship to the real human form. But the problem of identity goes far deeper. Stephen Glass, as a writer for The New Republic, created a website for a fake company, Jukt Micronics, for a story; Forbesexposed this lie, and countless others. But today, Glass might well have gotten away with it. Convincingly complete websites are easy to assemble. They don't even require human hands: Automated software cobbles together topical websites from republished copy scoured from the Web to trick Google into giving them free advertising revenue. And someone looking to hide their identity can now use proxy services to register domain names anonymously. For that matter, the Internet's domain-name system — the root of all online identity — is dangerously vulnerable. Earlier this year, security researcher Dan Kaminsky found a nearly fatal flaw that would allow hackers to hijacks visits to website and redirect viewers to alternate ones. That flaw has mostly been fixed, but who knows what other ones await discovery? By tricking the systems which route a request for a domain name — nytimes.com, for example — to the right server, a troublemaker might not just fake up a headline, but an entire alternate version of the Times online. Trust for media, old and new, continues to decline. Readers demand speed, punishing sluggish outlets by withholding their attention. Celerity replaces seriousness as a measure of authority. Who said what? Can you believe it? And does it matter, as long as you were the first to know?