Mobile analytics startup Mixpanel first caught the attention of Andreessen Horowitz by constantly showing up in the slide decks of entrepreneurs who were pitching the hot VC firm. “We were like: Hmmm, that company is pretty interesting!” says Peter Levine, a general partner at the firm. It was enough to set the wheels in motion for a $10.25 million Series A funding round, which Mixpanel is announcing today.

Also in on the round are PayPal co-founder Max Levchin, Salesforce.com chairman and CEO Marc Benioff, and Yammer chairman and CEO David O. Sacks. As part of the deal, Levine has taken a seat on Mixpanel’s board of directors.

San Francisco-based Mixpanel has a central role in a fast-emerging mobile industry that is still scurrying to plug the gaps in analytics, advertising, and targetting as Internet trends shift decisively to the small screen. With practically zero marketing spend, the Y Combinator company has already attracted 360 clients since its launch in July 2009. The company focuses on mobile engagement, tracking user “actions” within apps. It is set to track 7 million “actions” by the end of May. An action can include something as simple as a Path user sharing a photo to his or her timeline.

“We see this as being a core component to any company that is developing a mobile application presence,” Levine told me in a phone call.

Mixpanel, which charges on a month to month basis, lets its customers access finely segmented data, answering complex questions such as “Show me the age breakdown of people who are male, from the United States, and viewed the pricing page.” It also lets clients track user retention and analyze conversions.

This is a fast-growing space and is beginning to be cluttered with competitors, such as Bango, Flurry, Webtrends, Localytics. In just three months, Mixpanel has doubled the number of actions it tracks per month and increased revenue (which it hasn’t disclosed) by more than 50 percent. “We see this as being a core component to any company that is developing a mobile application presence,” says Levine.

Mixpanel’s founder, Suhail Doshi, says the company will use the Andreessen Horowitz funding to beef up its staff. In particular, he’s looking for more designers and a director of marketing. The company is so far 11 people strong, but, as we were ending our call, Doshi said he believed the company had just hired its 12 person. He hopes to use Andreessen Horowitz’s investment to grow the team to 100 within the short term and plans to do so by offering salaries that are far above the market rate in order to attract top talent.

Doshi believes Mixpanel’s advantage in part lies in its elegant user interface, which makes analytics tools such as Ominture look decidedly old hat. Its customers include video-sharing sites Viddy, SocialCam, and Airbnb, as well as niche social network Path.

[Disclosure: Andreessen Horowitz co-founder Marc Andreessen is an investor in PandoDaily.]