More under 40s: Mobilizers

Smartphone, $200. Protective case, $30. All that personal data on your mobile device? Priceless. It's little wonder that Lin, a professor who founded his mobile security business with $15,000 and a few grad students in 2005, is doing well. The Chinese company now makes the majority of its revenue overseas, and it's growing quickly -- revenues of $20 million jumped 125% last quarter, and they've risen more than 10-fold since 2008.

Khan, who worked for mobile giants like Motorola and Samsung in the past, signed on as Lin's co-CEO earlier this year. His mission? To raise NQ's profile and international reach beyond its current 204 million users in 150 countries. He expects the growing popularity of mobile payments and electronic health records will help. —Erika Fry

Dave Morin

Co-founder and CEO, Path

The Montana native and die-hard skier made a name for himself at Facebook, where he helped lead development of Facebook Connect and Facebook Platform, two key features that helped propel the social network to 1 billion monthly active users. Now Morin runs Path, the private social network on iPhone and Google devices that limits friends to 150 users. An active angel investor, he put money into Rupture, an online gaming network snapped up by Electronic Arts for $15 million in 2008, and the gift-giving app Karma, bought by Facebook earlier this year.

--JP Mangalindan

Cyriac Roeding

Co-founder and CEO, Shopkick

Credit the German entrepreneur and angel investor for launching Shopkick, one of the most innovative retail programs to come along in recent years. Shopkick's proprietary technology senses when users enter participating stores and rewards them with "Kick Bucks." The more Kick Bucks accrued, the more goodies users can claim, like cash back and gift cards usable at over 7,000 stores, including Target, Macy's, and Crate & Barrel. As Roeding tells it, increased foot traffic inevitably boosts store sales -- a veritable holy grail of retail, if ever there was one.

--JPM

Fared Adib

Product Chief/VP of product development, Sprint

The computer whiz saves the telecom company: As Sprint's product chief, Adib is making sure America's third-largest phone carrier doesn't go the way of the radio star. His CS chops and Silicon Valley connections have kept Sprint devices ahead of the curve -- it was the first with 4G, 3-D, dual-screens, and mobile payments, among others -- and its 56 million (and growing) customers happy.

--E.F.

Travis Kalanick

CEO and co-founder, Uber

Wanna get somewhere über-fast? Kalanick is banking on it: His hyper-hot app-based car service summons a sedan with the push of a button. The service, which costs more than a cab but saves you the hassle of hailing one, is posting 25% to 30% revenue growth, monthly. And with ambitions to expand to 100 cities around the world (from its current 17) by the end of next year, don't expect it to hit the brakes soon.

--E.F.

Meredith Perry

Founder, uBeam

This UPenn grad and onetime NASA intern may be only 23, but Perry's small startup, uBeam, which wirelessly transmits power, so impressed Yahoo CEO Marissa Mayer (herself No. 3 on the list) that she invested in the company 12 minutes after meeting Perry. Andreessen Horowitz, Founders Fund, and Zappos's CEO Tony Hsieh are also investors. With $750,000 in funding, Perry has said she's building out the technology as a consumer product (exactly what is yet to be determined). Gadget fans can hope to see it on shelves in Spring 2013.

--Colleen Leahey

Lyndon Rive

Co-founder and CEO, SolarCity

Lyndon Rive and his family want to change how we consume and pay for energy. Alongside co-founder and brother Peter, the COO and CTO, Rive has built six-year-old clean-energy company SolarCity into a leading force in the solar leasing space, with 26 operations centers across the U.S and more than 2,000 employees. He's got major backing too -- not only has cousin Elon Musk bet on the family business, but the company filed to go public in late April and Credit Suisse just doubled down on an earlier $100 million investment in July.

--Alex Konrad