Blogs, Facebook, and Twitter were supposed to liberate famous people from old-media gatekeepers. But John Mayer, Courtney Love, and others are teaching us that public figures are terrible at shaping their own image.

But who can be expected to do a good job as a one-man show in the swiftly professionalizing business of pretending to be an amateur? Even the gossips aren't doing the gossiping themselves. Even Perez Hilton is too busy hobnobbing with the people he ostensibly writes about to personally deface their photos anymore. It's understandable. Being yourself online is a full-time job. Ideally, for someone else.

The notion that blogs and Twitter will replace gossip has been around for a while. What's left for the tabloids if the stars reveal everything themselves? The gossip rags ought to fade away as celebrities interact with fans directly, and tell their stories their own way. Or so goes the webheads' theory.

But as Hollywood actors and musicians adopt Twitter en masse, the theory's getting a real-time test — and proving wanting. It turns out that media gatekeepers were really saving celebrities from themselves. As anyone who's written a magazine profile knows, what editors and readers want is an appealing, well-told story — not a numbing stream of trivia. And that means discarding far more material than one can ever use.

Facebook, Twitter blogs, and other media of the moment are a repository for that cutting-room floor — the ephemeral discards of mostly mundane lives. One man's trash is sometimes another man's treasure. But more often, it's just trash.

"It's inherently silly and it's inherently dumb," John Mayer, the musician and former Jennifer Aniston paramour told E! last week. Wise of Mayer to figure this out, though a bit late, since his Twitter addiction reportedly spurred his most recent breakup with Aniston. Mayer's smart enough to realize that Twitter is making him look like a fool to loved ones and strangers alike — but not smart enough to stop using it.

Courtney Love, meanwhile, is getting sued by a designer, Dawn Simorangkir, whose wares she once fancied, over ranting comments the professional Kurt Cobain widow left on MySpace and Twitter. Love has never been known for her self-control: Witness her unprovoked '90s-era rant about cheese, unleashed on an unsuspecting zine editor. But media which enable her to talk unfiltered 24/7 give us all too much insight into an obviously unbalanced mind.

Lindsay Lohan and Paris Hilton likewise have done themselves no favors in their blogging habits. Far from correcting their louche reputations, their overshares have cemented it.

Then there's the notion that fans would just sit back and receive all this information without comment. Jamie Spears, Britney's dad, is suing, a Britney Spears fan site, for allegedly invading his daughter's privacy. "I will destroy your ass!" Jamie Spears reportedly told BreatheHeavy webmaster Jordan Miller. (In fact, Jamie Spears may be mad about BreatheHeavy's aggressive questioning of the conservatorship arrangement under which he controls his daughter's finances.)

What's the solution? These people all need professional help. But since they're unlikely to spend the time they need on the psychiatrist's couch, they'll doubtless end up hiring assistants adept in social media. Ghostwritten Twitters are the hot new Hollywood must-have.

Every tweet will be media-coached. Every blog will be relentlessly edited — and then have typos inserted for authenticity. (Is that why someone pretending to be Rachael Ray consistently misspelled the cooking-show personality's name on a Yahoo blog?) The kids who are pretending to be celebrities on Twitter today will no doubt get paid to do it in the future.

Hilariously incompetent flack Jonathan Jaxson, who recently settled his legal spat with client Kim Zolciak of real Housewives of Atlanta, seems to be a pioneer here — in the sense that all pioneers get arrows in their back.

(Photo of Mayer by Getty Images; Spears by X17 Online)