Now that every celebrity has become a human home page, we are assailed by their brand extension at every turn. Each time Martha Stewart announces another new deal it makes me want to slip quietly away and take a nap. In addition to pretending to no longer run her magazine, television and merchandising empire, she has now committed to a 24-hour channel with Sirius satellite radio, a daily NBC-TV cooking show and a spinoff of "The Apprentice." Not content with this frenzy of rebirth, she has stirred up another feds flap — this one by turning up at the Time 100 Most Influential People dinner at Jazz at Lincoln Center’s Time Warner Center instead of staying tucked up at home in her 450-thread-count sheets and locator bracelet.

Doesn’t Martha realize how lucky she is not to have to show up at the Time 100 Most Influential People dinner? Doesn’t she know how envious Katie Couric must be of that ankle bracelet right now? House arrest must sound to Katie like a trip to Fantasy Island — a perfectly acceptable excuse not to get up at 4 in the morning with a perky smile to face a firing squad about whether she should have worn a short skirt or pants on the air. But no, there’s a threat that NBC may soon be extending the Katie brand again.

"I don’t know why Brian Williams isn’t blogging right now," NBC Universal Television Group President Jeff Zucker mused aloud the other day at a conference on high-speed Internet use, adding that he could envision a blog for Katie Couric, too. In addition to Katie’s predawn call, the pit stops at the Vatican or wherever, the torturous glamour maintenance, the fundraising for colon cancer, plus raising two daughters without a husband, she’s supposed to carve time out to blog away with chummy girl-next-door attitude for her fickle public? Soon we’ll open the fridge door and behold a singing, dancing Katie Couric. Isn’t there a limit to what $13 million a year will buy a corporation?

Well, no actually. Celebrities who hired themselves big-time agents to turn them into brands are now being sucked dry by their own demands. In Hollywood, as Tad Friend reported in his New Yorker profile of William Morris President Dave Wirtschafter, agents like to talk about artists taking over an "environment," a "universe," a "space" such as the "musically capable girl-band space inhabited by the Donnas." Or "Suddenly, the Sarah Michelle Gellar space is meaningful."

But the wholesale commodification of talent means that the person occupying that "space" has to be manifest in every available outlet, orifice and time slot. It’s a fab new world for stars with a tiny or tenuous relationship with talent. Except for the odd wardrobe meltdown or collapse from anorexia or substance abuse, they thrive on it. There’s a whole raft of reality-show divas on the covers of magazines like Us and In Touch who have been minted for this very need. It’s the human equivalent of straight-to-video: Skip the talent part and go directly to fame. But the genuinely, or even minimally, creative artist or performer who carries around the usual bundle of frail nerves, ill temper and gloomy introspection learns that the multimedia universe is becoming a place where you can sicken and die from the sight of your own reflection.

How some of the nervier artists feel in the land of opportunity is well illustrated in an interesting little documentary directed by Rosanna Arquette, "All We Are Saying," that’s at the Tribeca Film Festival. It’s about musicians, but it could just as well be about filmmakers or writers or painters, and it features exceptionally honest and heartfelt interviews with, among others, David Crosby, Sting, Stevie Nicks, Joni Mitchell and members of Radiohead and Aerosmith. Many of these aging rebels, it seems, feel lost and buffeted by the multimedia, synergistic, conglomeratized, marketing-driven business behemoths that have shut down the options of where they can work while amping up the demands for product and promotion. They all seem to long for a creative connection in a world where the energy is only on the selling side of the business.

"The whole thing is freakin’ chaos," says Radiohead’s Thom Yorke, who has started to resemble a hipper, more elfin version of Uncle Fester from "The Addams Family." "It’s really a good time to go and stand in the shadows again."

"A couple of years ago," a grizzled Crosby tells Arquette, "you had one-quarter of the music business owned by a whiskey company, who then sold it to a French water company, neither of whom would know a song if it flew up their nose and died. They haven’t a clue. They know they moved 40,000 pieces out of Dallas this month, but they have no idea pieces of what."

Joni Mitchell, now a wised-up, beat-up old hippie, likens herself to a horse who can’t go over the jump anymore. Thirty-two years ago, in her great song "Free Man in Paris," she prophetically bemoaned "the work I’ve taken on / Stoking the star-maker machinery / Behind the popular song." Today the machinery is so overwhelming it’s crippling her. She starts to write a song; then the thought of the gantlet of press — "which got dumber and dumber and dumber and shallower and shallower and shallower and more and more hostile" — chases away her muse.

These voices are especially striking because you so rarely hear big-time talent talking this way about their work. It doesn’t fit the paradigms of celebrity journalism. Artistic angst — which, after all, only the luckiest people on Earth are in a position to feel in the first place — is not what readers of the fabloids want to hear about. They want to hear about the marital, romantic and weight-gain sufferings of the stars.

The emaciated frame and sad-clown makeup of Michael Jackson as he drifts into court each day in Santa Maria is like the picture of a music industry Dorian Gray. This is what it looks like when you are all burned up from renting out your soul to the beast of supply and demand, its quest for new looks, new sounds, new stunts, new reinvention — all to become the Lord of Neverland. Perhaps it’s not really Michael Jackson at all under that ubiquitous umbrella. It’s just the person occupying the Michael Jackson "space."