(FORTUNE Magazine) – In Silicon Valley, starting a company and selling it before it went public used to be a last resort. It meant admitting that you wouldn't get to be the next Bill Gates or Larry Ellison. Most of the time, it meant you wouldn't even get to be rich.

No longer. Selling out is now called an "exit strategy," and, for the current breed of Netrepreneurs, a mighty good one. It's creating a new generation of "serial entrepreneurs," as one of them dubs himself. Inspired perhaps by Jim Clark--famed for his success in starting businesses such as Netscape and then leaving others to run them for the long term--they've begun building and selling companies with unprecedented speed.

Typically, they're doing it on a smaller scale than Clark (for more on Clark, see "What the Heck is Healtheon?"). The companies they're unloading often consist of little more than one well-developed innovation or software feature. As the bigger, public Net companies scramble to get an advantage of even a few months in bringing new features to market, they create tremendous incentives to sell out fast. "In the '80s, selling out was considered a failure," says Ted Barnett, who sold When.com, his online calendar service, to America Online in 1998. "I remember working at a startup where our hope was to one day go public and be worth $100 million. Now an acquisition can be worth $500 million."

Even if it's not $500 million, the take can be substantial. In fact, while Silicon Valley entrepreneurs still give lip service to the hope of "building the next Microsoft," the reality is that many are now content simply to sell out to Microsoft.

Take Mark Goldstein, now CEO of BlueLight.com, Kmart's Net shopping venture. BlueLight is his fourth online creation--an unusually fecund output given the short history of the Net. The first, Reality Online, which Goldstein co-founded in 1987 and sold to Reuters in 1994 for more than $20 million, was an early attempt at creating an online stock brokerage. The second, Net- Angels, developed search tools and was sold to a company called Firefly for $2 million in early 1997, six months after unveiling its technology. (Firefly itself sold out to Microsoft in 1998.)

The big score came with Goldstein's third company, Impulse Buy, which created a shopping engine that let merchants update specials and sales, and a deal ticker that let customers take advantage of them. Started in 1998, Impulse Buy was acquired by Inktomi in 1999 for $110 million in stock.

Goldstein compares himself to a movie producer turning out film after film. "Silicon Valley went Hollywood over the last few years," he says. "We're putting on productions. Our role is to find the best screenwriters, the best actors, bring the team together and create a great experience."

Goldstein may be faster than most. But right now Silicon Valley is filled with entrepreneurs working on their second Net production, and a few on their third. Sabeer Bhatia, the founder of Hotmail--the company whose $400 million acquisition by Microsoft was among the first megabuyouts--is working on an e-commerce startup, Arzoo. Meanwhile, Steve Perlman, the technologist who in quick succession co-founded Catapult Entertainment (it was sold to the online community company Hearme.com) and WebTV (now owned by Microsoft), has graduated from running companies and is starting an incubator for new technologies.

But as the founders move on to their next ventures, what happens to their companies? Sometimes, as with Hotmail, the free e-mail service bought by Microsoft, they become the spearpoint of a bigger company's strategy. But more often they are stripped for parts; the buyer is interested not in the car, but only in the transmission. Reality Online still exists as a Reuters unit devoted to handling the back-end operations of online brokerages. NetAngels has disappeared into Microsoft's suite of tools, along with Firefly, and Inktomi used some of Impulse Buy's tools to build its own e-commerce offerings.

Even the most promising ideas can disappear into the maw of a big company until few surviving traces of them can be seen. Amazon paid $170 million in stock in 1998 to buy two-year-old Junglee, a company that had built one of the first services that let shoppers compare prices across the Net. But now the idea of comparing prices isn't mentioned on Amazon's site. And while you can still find the remnants of the Junglee service and use it to search other merchants' sites, you'd be hard-pressed to find the features. Naturally, Junglee's founder, Rakesh Mathur, is starting a new company, a search service called Purple Yogi.

If a Net company gets sold for a fortune, and nobody notices what happens to it, did it ever really exist? Does anyone even care? Not much, in today's Silicon Valley. If getting to your next payday means selling your (corporate) baby, so much the better. The next Microsoft can wait for the next guy.