Silicon Valley has had a knack for finding at least one of these remarkable pairings just about every decade. They’re the creators of new industries  chips, PCs, servers, Web sites and ad-fueled search systems  on which others build. But lately, companies started by E.I.R.’s have done yeoman’s work for the venture capitalists.

The investment firm New Enterprise Associates, for example, hit it big last year when the storage giant EMC bought Data Domain for $2.3 billion, the largest acquisition in 2009 of a venture-backed technology company. (The average deal that year was just $144 million.)

The Data Domain story grew out of a chance encounter. Kai Li, who would be a co-founder of the company, was on sabbatical from his job as a computer science professor. He had been thinking about some ideas for a start-up when he ran into an old friend from New Enterprise. A couple of chats later, he was an E.I.R.

Similarly, the biggest public offering of a venture-backed technology company in 2007 was that of MetroPCS, which raised $1.2 billion. It was started by Roger Linquist when he was an E.I.R. at the venture capital firm Accel.

Image Kevin Epstein, a former entrepreneur in residence, says the role lets people “be creative and think of new ideas.” Credit... Peter DaSilva for The New York Times

A host of other flashy companies have recently emerged from the E.I.R. ether. Zimbra, an e-mail software start-up, was sold for $350 million to Yahoo in 2007. (In a very different economic climate this year, it was sold again to VMware for a reported $100 million.) Then there’s Cloudera, one of the most-watched start-ups in Silicon Valley. It seeks to bottle the analytical smarts on which Google and Yahoo rely to understand their users’ behavior and sell the product to large corporations dealing with torrents of data. Cloudera came into being at Accel, where a pair of E.I.R.’s worked after having left Yahoo and Facebook.

Venture capital firms are closely held, so there is no data on the number of companies that the E.I.R. process has created  or on how many of them have succeeded. But top firms say a new company is formed about 50 percent of the time. The rest of the E.I.R.’s will either take on a job at an existing company in the venture capital firm’s stable or go their own way.