Google's attempt to build a home for personal health records online could potentially be more lucrative than Web search, says a top equity analyst.

After months of talk, Google last week showed its Health program at a conference in Orlando. Google said it wouldn't start out selling ads but wouldn't rule it out. Google Health is expected to launch this year.

Gene Munster, an analyst with Piper Jaffray, believes ads will happen. "Advertisers would pay absurd amounts of money to be seen when someone wants to, say, refill a subscription online," he says. "This is more lucrative than commerce-related search."

David Kessler, a former head of the Food and Drug Administration, calls the ability to access health histories a "major undertaking. I've run a hospital and am a physician, and I can't even keep track of my family's medical information." He is one of more than 20 experts advising Google on its health program.

That Google — and Microsoft, whose HealthVault launched in October, among others — are trying to get medical records digitized is "the beginning of a new chapter in healthcare," Kessler says.

Last week, Google announced a pilot program with The Cleveland Clinic.

"Many people have never even seen their health records, let alone their prescription history and lab results," says Google Vice President Marissa Mayer.

Mayer says the information can only be shared between a health provider and patient, though future versions will let you share with friends and family via a password.

Since announcing the program last week, privacy issues have fueled a lot of debate. Among potential scenarios: An employer finds your health records online and fires you over something in your medical history. "But those are human actions," says Dr. Molly Coye, CEO of non profit HealthTech, and another Google adviser. "They have nothing to do with the technology."

Andrew Rocklin, a principal with Diamond Management & Technology Consulting, says paper records are more likely to be tampered with. "There's a concern about having this online because it's new and not part of our everyday lives, but as people get more used to it, they'll see the benefit," he says.

Sean Nolan, head of Microsoft's health solutions group, says he's signed up 17 partners to work with HealthVault, and expects to add New York Hospital and Johns Hopkins Hospital in the coming months. "The idea that I can have a persistent data connection with my doctors is super exciting," he says.