Omar Hamoui has been on both sides of the fence. He was a starving entrepreneur, hungry for funding and validation. And now he’s a venture capitalist as a partner at Sequoia Capital, chasing after entrepreneurs who are sometimes too busy to talk to him.

Hamoui painted a picture of that transition in a conversation with Rich Wong, partner at Accel Partners, at our MobileBeat 2013 conference today. Hamoui cofounded AdMob in 2005 and Wong’s Accel became one of his investors. The self-serve mobile advertising platform took off and Google bought the company for $750 million in 2009. Hamoui left and started his own angel investments. Then a few weeks ago he joined Sequoia Capital¬†as a partner.

Hamoui now has to care about life beyond advertising, and he is running after entrepreneurs. He said on stage that he recently talked to an entrepreneur who said he didn’t have much time to talk because he had to focus on running the business.

“I look for how passionate they are about what they are doing,” Hamoui said.

He shared that passion in 2005, when he was starting AdMob. He moved his family to Philadelphia to get an MBA at the Wharton School of business. He was working on a WAP photo-sharing tool dubbed Photo Chatter. He couldn’t find distribution for it on mobile channels as they existed at the time on carrier networks.

“I thought there should be a self-serve way to serve ads,” he said.

Then AdMob was born. Hamoui quit business school mid-way through and moved back to Silicon Valley. He raised money, even though he didn’t know the answers when VCs asked him about competitors who were doing the same thing. AdMob was ready when the iPhone launched in 2007.

“When the iPhone came out, to me, that was the phone we were waiting for,” he said.

Today, Hamoui has a focus on mobile investments. He says entrepreneurs should clearly be focused on iOS and Android.

He said he felt that the fire-and-forget style of angel investing didn’t suit him, and he wanted to have ongoing relationships with the entrepreneurs. At Sequoia, he said that he’ll work closely to help entrepreneurs build their companies.

“That’s what drew me into the VC world,” he said.