Here is a look at some of these pioneering investors and what they are looking at now.

KEVIN EFRUSY, ACCEL PARTNERS

Efrusy did research and sourced Accel's original investment in Facebook, although Accel partner Jim Breyer sits on Facebook's board. Since then, Efrusy has invested in businesses ranging from deal-a-day company Groupon to financing company Capital Access Networks.

Currently, he spends a lot of time on flights to Brazil, where he made several investments last year, including: online travel site Despegar; brain-development company Mind Lab; online retailer Shoes4You; and online craft marketplace Elo7.

CHI-HUA CHIEN, KLEINER PERKINS

Chien was an associate at Accel Partners while getting an MBA at Stanford University, told the partners at Accel about Facebook, and did some research that led to Accel's investment.

In 2007, Chien joined Kleiner Perkins, which has a number of high-profile consumer-Internet investments, many handled by Chien. The firm made an investment in Facebook around early 2011, a spokeswoman for Kleiner Perkins said. Chien was involved in Kleiner's investment in microblogging service Twitter, and sits on the boards of influence-gauging service Klout, social-network Path, and proximity-based marketing service Zaarly.

One departure from his consumer-Internet focus is Home Value Protection, which insures homeowners against falling home values. The investment was inspired in part after watching fellow Californians struggle to hold onto homes in the early 1990s recession as well as today, he said.

MATT COHLER, BENCHMARK PARTNERS

Cohler left a job at LinkedIn in early 2005 to become Facebook's seventh employee. In 2008, he left to join Benchmark Capital, which has not invested in Facebook.

At Benchmark, he has invested in a couple of companies run by Facebook chums. They include business-collaboration service Asana, co-founded by Facebook alumni Dustin Moskovitz and Justin Rosenstein, and question-and-answer service Quora, founded by Facebook alumni Charlie Cheever and Adam D'Angelo.

He also led Benchmark's investment in photo-sharing service Instagram, which Facebook bought last month for $1 billion.

But he is also thinking farther afield. Cohler has invested in China-based Baixing, an online community and marketplace; Germany-based ResearchGate, a social network for scientists; and Brazilian deal service Peixe Urbano.

PAUL MADERA, MERITECH CAPITAL

Madera used to fly F-16s as a U.S. Air Force pilot. His introduction to finance came via stints at Morgan Stanley and Montgomery Securities before co-founding Meritech in 1999.

Normally, the firm gets involved in a start-up company's later stages, expecting a return of three times capital, much lower than the 10 times or so earlier-stage venture capital firms seek.

Madera's eclectic background has resulted in investments to match. Some of his other bets include: DealerSocket, a customer-relations management service for auto dealers; Glaukos, a glaucoma-specialized medical-services company; Wonga, a British short-term consumer-loans company; and Yammer, a social-network for business.

DAVID SZE, GREYLOCK PARTNERS

At the time he made his Facebook investment, Sze already had several years as a partner at Greylock under his belt, allowing him to invest in business social-network LinkedIn.

Today, he is investing in companies such as Path, the social network founded by Facebook alumnus Dave Morin, and WhoSay, which handles personal media management for celebrities, and is quick to tip his hat to the overall Greylock team.

"We don't do anything in isolation," he said. "It's a gang tackle."

Before joining Greylock, he did stints at Internet-services and content company Excite, Inc. and games company Electronic Arts. His sister is artist Sarah Sze, who is representing the United States at the Venice Biennale art fair next year.

(This story corrects 6th graf to say Kleiner Perkins made an investment in Facebook.)

(Reporting By Sarah McBride; Editing by Will Dunham)

Stocks treated in this article : Electronic Arts Inc., Groupon Inc, Linkedin Corporation