As Google grows, how much does it know about you?

Google is at once a powerful search engine and a growing e-mail provider. It runs a blogging service, makes software to speed Web traffic and has ambitions to become a digital library. And it is developing a payments service.

Although many Internet users eagerly await each new technology from Google Inc., its rapid expansion is also prompting concerns that the company may know too much: what you read, where you surf and travel, whom you write.

"This is a lot of personal information in a single basket," said Chris Hoofnagle, senior counsel with the Electronic Privacy Information Center. "Google is becoming one of the largest privacy risks on the Internet." Not that Hoofnagle is suggesting that Google has strayed from its mantra of making money "without doing evil."

Rather, some privacy advocates worry about the potential: The data's very existence -- conveniently all under a single digital roof -- makes Google a prime target for abuse by overzealous law enforcers and criminals alike.

Through hacking or with the assistance of rogue employees, they say, criminals could steal data for blackmail or identity theft. Recent high-profile privacy breaches elsewhere underscore the vulnerability of even those systems where thoughtful security measures are taken.