Born in suburban Paris in 1974, Mr. Grinda graduated from Princeton in 1996 with a degree in economics. He worked as a consultant at McKinsey & Company for two years before moving back to France to found an online auction start-up funded by the business magnate Bernard Arnault, which Mr. Grinda sold in 2000.He returned to the United States, where he co-founded Zingy, a mobile phone ringtone and game maker, which fetched $80 million in a 2004 sale. After that, he was a founder of OLX, a Craigslist-like service that has become one of the largest global classified websites.Now he is an entrepreneur and angel investor, with more than 200 investments to date, who visits start-ups in Berlin, Paris, New York, San Francisco and other cities.