IT seems a hazy memory, but Keith Wilson, a spiky-haired club promoter, can recall what it was like before MySpace -- about two years ago. Back then people had normal names like ''Joe'' or ''Keith.''

''People don't call me 'Keith,''' he said, straining to be heard as cascades of power chords rumbled from the stage at Boardner's, a club just off Hollywood Boulevard, on a mid-August Wednesday night. ''They call me 'Keith 2.0,' because that's my MySpace name. That guy over there, he's 'Joeymachine.' Everyone has a MySpace name now.''

Dozens of extravagantly tattooed Hollywood urchins waited in a line down the sidewalk to join a sweaty throng inside the club, which that night was playing host to a weekly live rock series Mr. Wilson promotes called Club Moscow. The fans were there, he said, because they heard about the show on MySpace. The bands they were listening to were building a following by posting home pages on MySpace.

''I conduct my entire business through MySpace,'' said Mr. Wilson, 25, who relies on MySpace.com, a social-networking Web site, to orchestrate his professional and personal schedule and is no longer sure he needs an America Online account or even a telephone. ''I haven't made a flier in years,'' he said.

Created in the fall of 2003 as a looser, music-driven version of www.friendster.com, MySpace quickly caught on with millions of teenagers and young adults as a place to maintain their home pages, which they often decorate with garish artwork, intimate snapshots and blogs filled with frank and often ribald commentary on their lives, all linked to the home pages of friends.

Even with many users in their 20's MySpace has the personality of an online version of a teenager's bedroom, a place where the walls are papered with posters and photographs, the music is loud, and grownups are an alien species.

Although many people over 30 have never heard of MySpace, it has about 27 million members, a nearly 400 percent growth since the start of the year. It passed Google in April in hits, the number of pages viewed monthly, according to comScore MediaMetrix, a company that tracks Web traffic. (MySpace members often cycle through dozens of pages each time they log on, checking up on friends' pages.) According to Nielsen/NetRatings, users spend an average of an hour and 43 minutes on the site each month, compared with 34 minutes for facebook.com and 25 minutes for Friendster.

''They've just come out of nowhere, and they're huge,'' David Card, a senior analyst with Jupiter Research, said of MySpace. ''They've done a number of things that were really smart. One was blogging. People have been doing personal home pages for as long as the Internet's been around, but they were one of the first social networks to jump on that. They've also jumped on music, and there's a lot of traffic surrounding that.''

''And,'' he added with delicacy, ''I think a lot of their traffic comes from the pictures. I don't think there's anything X-rated, but there are lots of pictures of college students in various states of undress.''

Even the founders seem taken aback. ''I don't want to say it's overwhelming,'' said Tom Anderson, 29, who created MySpace with Chris DeWolfe, 39, ''but I see these numbers coming out, I keep thinking, it must be a mistake. How can we pass Google? I mean, my mom knows Google, but she doesn't know MySpace.''

One adult who has paid attention is Rupert Murdoch, the chief executive of the News Corporation, which agreed in July to pay $580 million to buy the site's parent company. At the time News Corporation executives explained the investment by citing MySpace's surging popularity among young people, who are often difficult to reach through newspapers and television.

The growth of MySpace -- which is free to users and derives revenue from banner ads appearing on top of each page -- is all the more striking because at its core it doesn't offer anything particularly new. Mr. Anderson, who has a master's in film studies from the University of California, Los Angeles, played guitar and sang in a band called Swank. He conceived the site while helping run an Internet marketing company he started with Mr. DeWolfe.

Internet commerce was then still recovering from the bursting of the bubble in 2000, although social networking sites like Friendster and Facebook were enjoying fad status with users who joined to track down old friends and troll for dates.

Mr. Anderson's idea was to expand the social-networking model into a one-stop Web spot, incorporating elements from other sites popular with the young: the instant-message capabilities of American Online, the classifieds of Craigslist.com, the invitation service of Evite.com and the come-hither dating profiles of match.com. The founders spread the word about MySpace through friends and anyone they happened to meet in Los Angeles at bars, nightclubs or rock shows.

''Since we're telling people in clubs -- models -- suddenly everyone on MySpace looks really pretty,'' recalled Mr. Anderson, who with his trucker hat and sideburns looks as if he could be gigging in a club himself later on. ''That wasn't really the plan. It just kind of happened.''