Known as the unicorns, these private technology companies are worth $1 billion or more, thanks to an influx of cash from venture capital firms, hedge funds, private equity firms and mutual funds.
But alongside the Wall Street money flowing into these companies' coffers, a familiar set of names is operating behind the scenes by advising, investing in and, in some cases, founding the unicorns.
The PayPal Mafia - a nickname given a group of alumni of PayPal, the payments company that went public in 2002 and was acquired by eBay - has its hands in many, if not most, of today's most valuable private tech companies.
Their enduring influence, more than a decade after they made their first fortunes, speaks to the tightknit social fabric of Silicon Valley's technology industry and to the trust new entrepreneurs place in those who have succeeded before them. And now, the PayPal group's close ties with the current crop of unicorns - a collection of some of the most valuable technology startups ever seen - suggest its influence is undiminished.
Peter Thiel, a co-founder and former chief executive of PayPal, is an investor in companies including Airbnb, the big-data company Palantir, the spaceflight provider SpaceX and the payments company Stripe, four of the most valuable tech companies in Silicon Valley today.
And Keith Rabois, the former head of business development at PayPal who is now a partner at Khosla Ventures, holds shares in Airbnb, Stripe and Palantir, to name a few.
The shared experience of PayPal alumni makes their advice - and money - particularly valuable to young entrepreneurs. An online payments provider founded in the 1990s, the company succeeded despite going public shortly after the terrorist attacks of Sept. 11, 2001, even as the economy was still reeling from both the attack and the collapse of the dot-com bubble.
"PayPal was an extreme experience in survival against all odds, over and over again, with enormous and lasting success," said Max Levchin, PayPal's co-founder and chief technology officer. "Like veterans of an intense military campaign, we fall back on lessons learned and relationships established in our early 20s."
After PayPal was acquired by eBay in 2002, the alumni of PayPal emerged as among the few willing to invest in new tech startups.
"We went from this bunch of misfits to the center of the ecosystem," Rabois said. "Entrepreneurs needed capital, and the only place to get the capital was from us."
Even as the members of the alumni group have gone on to found new companies and take roles at venture capital funds, they have continued to invest in each other's companies and in new entrepreneurs.
"There's a vicarious reliving of our old experience by working with new, young teams," said Roelof Botha, a partner at Sequoia Capital who was head of business development at PayPal and has invested in Square. "The surest path to dementia is to stop working when you're young."
Part of the reason this small cabal of friends - all men, mostly white, under the age of 50 - remains at the center of the action in Silicon Valley is that, among the entrepreneurial elite, success begets success.
"There's a network effect to these things," said Stoppelman, who today is chief executive of Yelp, the user review site he co-founded. "If you have a name that's associated with success, people will seek you out. Why do smart people go to Harvard? Because previous smart people went to Harvard."
Or in this case, entrepreneurs want PayPal alumni to invest in their startups because PayPal alumni have invested in previously successful entrepreneurs. For more than a decade, the PayPal group has been integral to the founding or financing of many of the best-known startups, making them even richer in the process. Thiel, who now runs venture and hedge funds, was one of the earliest investors in Facebook. Several PayPal alumni invested in Yammer, which was acquired by Microsoft for $1.2 billion in 2012.
Yammer was also founded by a former PayPal executive, David Sacks, PayPal's former chief operating officer. And, indeed, the group has not only funded many of today's successful technology companies but also has continued to create them.
LinkedIn, now worth $32 billion, was co-founded by Reid Hoffman, another former PayPal chief operating officer. Stoppelman and another PayPal alum, Russell Simmons, co-founded Yelp, now worth $3.5 billion. And Elon Musk, who co-founded the company that became PayPal, subsequently started Tesla, worth $23 billion, and SpaceX, a unicorn valued at $12 billion.
"We have a very good collective résumé," said Scott Banister, a former PayPal board member, explaining the sustained influence of the group. "It's not just that you're associated with the company, it's that you're associated with the other people associated with the company."
After leaving PayPal, Banister co-founded an email service, IronPort, which he sold to Cisco Systems for $830 million.
Investing in new entrepreneurs today allows these seasoned veterans of the technology scene to stay close to the ground, where new entrepreneurs are trying to bootstrap their way to fortune and fame.
Levchin sold a social gaming company, Slide, to Google in 2010. He recently started a payments company, Affirm, backed by several former colleagues.
"At Yelp, every time it was time for a funding round, Peter Thiel was my go-to adviser," Stoppelman said. "When it came to thinking about the product and growth strategies, Max was my day-to-day. For broad thinking, I would go to Keith."
But investing in startups is inherently risky. While PayPal alumni have managed to back several big winners, the specter of failure always looms large.
"Anytime I write an angel check, I say, 'This is probably the last time I will see this money,' " Stoppelman said. "It hurts just as much to lose $25,000 as it would to lose $1 million."
For now, however, the collective résumé of the PayPal Mafia is largely unblemished.
© 2015 New York Times News Service