(FORTUNE Magazine) – Groucho Marx once said he'd never want to be part of a club that would have him as a member. The members of this club know exactly how he felt. These 20 victims of the tech bubble--as well as Mediaplex's Greg Raifman (see previous story)--are among those who have had their paper fortunes shredded by ten figures over the past 18 months or so. The biggest loser? MicroStrategy's Michael Saylor, who saw a staggering $13.53 billion vanish.

To compile our list, we looked up the biggest shareholders of technology companies that went public after Netscape did (on Aug. 9, 1995). Using data from Thompson Financial and Bloomberg, we then filtered out their stock options and indirect holdings (such as shares held in a trust) and subtracted their direct holdings as of the week ended May 18 from their direct holdings when the stock was at its peak. Sales and gifts of direct stock were counted against losses. If a company had two or more billion-dollar losers, we chose the one who owned the most shares.

But before you shed a tear for these guys, remember that most of them are still centimillionaires. Which is a good thing, since dues at the Billionaire Losers Club can get pretty steep.

1 Michael Saylor Chairman and CEO, MicroStrategy Lost $13.53 billion Saylor--whose massive losses (he has $179 million in direct stock left) prompted him to scrap plans to build a Versailles-like mansion on the Potomac--told The New Yorker in April 2000, "I just hope I don't get up one day and have to look at myself in the mirror and say, 'You had $15 billion and you blew it all. There's the guy who flushed $15 billion down the toilet.'"

2 Jeffrey Bezos Chairman and CEO, Amazon.com Lost $10.80 billion "A company isn't its stock," Time's 1999 Person of the Year (whose direct Amazon holdings are now worth $1.7 billion) told the Seattle Post-Intelligencer last year. "And stock isn't the company."

3 David Filo Co-Founder and Chief Yahoo, Yahoo Lost $10.31 billion At least the taciturn Filo, who now has less than $800 million of Yahoo stock, isn't alone: Co-founder Jerry Yang (who owns a bit less stock than Filo does) lost almost as much money.

4 Naveen Jain Chairman and CEO, InfoSpace Lost $10.13 billion "I will get those billions back and then some," insists Jain, who founded the software company in 1996. "The billions [lost] will be like pocket change."

5 Jay Walker Founder, Priceline.com Lost $7.51 billion Watching Priceline stock plummet (his direct holdings are currently worth $103 million) is "a disappointment," Walker told Newsweek last October, "but not the end of the world."

6 Pierre Omidyar Chairman, eBay Lost $5.00 billion He's one of the lucky ones: Omidyar still owns a none-too-shabby $3.65 billion of eBay stock. Even after fulfilling his vow of donating all but 1% of his wealth to charity by 2020, he'd have, given his current wealth, tens of millions left over.

7 Pehong Chen Chairman, CEO, and President, BroadVision Lost $4.86 billion Though Chen's holdings have been slashed to $337 million, he still hasn't sold a single BroadVision share: "I think it could be worth a lot more sometime in the future."

8 Robert Glaser Chairman and CEO, RealNetworks Lost $4.33 billion Battle of the billionaire losers: Glaser's RealNetworks is now launching an online music service to slug it out with Michael Robertson's MP3.com.

9 Keith Krach Chairman, Ariba Lost $2.92 billion "Sometimes you feel like a fly in a nudist camp," observed the software maker's founder in July 2000. "You don't know where to land first because there's so much opportunity out there."

10 William Kaiser Director, Red Hat Lost $2.49 billion A venture capitalist with Boston's Greylock who supplied a big chunk of seed money to Red Hat, Kaiser doesn't have time to lick his financial wounds: He sits on the boards of nine other companies he has funded.

11 Daniel Lewin CTO, Akamai Technologies Lost $2.30 billion "I never wanted to start a company," the Israeli ex-paratrooper told the Jerusalem Report back in July 1999.

12 Walter Buckley III President and CEO, Internet Capital Group Lost $2.19 billion At the company's peak in early 2000, Buckley often compared it to Jack Welch's General Electric. Since then, ICG's stock has fallen 98.5%.

13 Dale Skeen CTO and Director, Vitria Technology Lost $2.00 billion For Skeen, taking a bath in e-business software is a family affair: Wife JoMei Chang, Vitria's president and CEO, has lost about $1.6 billion herself.

14 Victor Shear Chairman and CEO, InterTrust Technologies Lost $1.44 billion "We are a company that has understood, defined, and invented the way the world is going to operate," Shear declared in April 1999.

15 Michael Robertson CEO, MP3.com Lost $1.43 billion When asked how it feels to lose more than a billion dollars in his Web music company, founder Robertson told FORTUNE, "I never really considered that I had it."

16 Monte Zweben Chairman and CEO, Blue Martini Software Lost $1.20 billion If worse comes to worst, Zweben has a career fallback: He told FORTUNE last year that he aspires to be a jazz guitarist.

17 Alain Rossmann Chairman and Executive VP, Openwave Systems Lost $1.11 billion "These guys aren't motivated by money," says spokesperson Natalie Sequeira of Rossmann and his Openwave colleagues. "They're technology geeks. They do it for the love of it."

18 David Hitz Executive VP, Network Appliance Lost $1.09 billion Hitz once bragged that "there's no reason we can't be a Cisco-sized company." Or did he mean food distributor Sysco, whose $19 billion market cap is now more than twice Network Appliance's?

19 Mark Tebbe Chairman, Lante Lost $1.03 billion "People get too hung up on their net worth," insists Tebbe, whose direct Lante holdings now total $16.8 million. "It's never affected me. I have more money than I ever had as a kid, and I was happy as a kid. So I'll be happy now."

20 Kevin O'Connor Chairman, DoubleClick Lost $1.02 billion "We don't talk about stock. It's just a bad, bad thing," said O'Connor in October 1999. "I don't think my job is to maximize shareholder value at some point in time."