A few years ago, I walked into an Internet cafe in Tibet's capital, Lhasa. There were no Chinese soldiers in the room and no visible government censors nearby. A sign on the wall, however, reminded users that China's all-seeing eye had not disappeared. "Do not use Internet," the warning instructed, "for any political or other unintelligent purposes."

Since then, China's ruling regime has perfected the science of controlling what the Chinese can read or write on the Internet to such a degree that it has become the envy of tyrants the world over. We might have expected that from a regime that has proved it will do whatever it takes to stay in power. What we never expected was to see Google, the company whose guiding motto is "Don't be evil," helping in the effort.

Google's decision to help China censor searches on the company's new Chinese Web site is not only a violation of its own righteous-sounding principles, and it's not just an affront to those working to bring international standards of human rights to the Chinese people. No, Google's sellout to Beijing is a threat to every person who ever used Google anywhere in the world.

That's no exaggeration. Google saves every search, every e-mail, every fingerprint we leave on the Web when we move through its search engine, or its Gmail mail service, or its fast-growing collection of Internet offerings. Google knows more about us than the FBI or the CIA or the NSA or any spy agency of any government. And nobody regulates it. When a company that holds digital dossiers on millions of people decides profits are more important than principles, we are all at risk.

Google will now participate in a censorship program whose implications, according to Harvard's Berkman Center for Internet and Society, "are profound and disturbing." The Chinese government blocks thousands upon thousands of search terms — including "censorship."

To be fair, Google is hardly alone in capitulating to Beijing's rulers to gain a Web share of China's 1.3 billion inhabitants. The country's tantalizing market has tested the ethics of many a Western corporation — and almost all have failed the test. That is particularly true in the Internet business.

Just last year, Yahoo helped Beijing's Web goons track down the identity of a Chinese journalist who wrote an e-mail about the anniversary of the 1989 Tiananmen Square massacre — a massacre of Chinese democracy advocates. The journalist, Shi Tao, was sentenced to 10 years in prison. Reporters Without Borders labeled Yahoo an "informant" that "collaborated enthusiastically" with the Chinese regime. Microsoft, too, plays by the dictatorship's rules. Bloggers on MSN's Chinese service cannot search words such as "democracy" or "freedom." Internet users in China cannot read or write about anything that even hints of opposition to the ruling Communist Party. Even pro-Western commentary can trigger a block. And forget anything about Tibet or the Dalai Lama. Chinese bloggers, incidentally, must all register and identify themselves to authorities.

The often-stated desire to "do good" and make the world a better place was one of the traits that endeared Google to the public. It was one of the reasons we trusted it to guard the precious and valuable contents of the company's thousands of servers.

Now Google has become a company like so many others, with an eye on the bottom line before anything else. The company has decided to help China's censors even as it fights a request for records from the U.S. Justice Department. Skeptics had claimed Google was resisting the request to protect its technology, rather than to protect users' privacy. That explanation now sounds more plausible than ever.

We've long known about China's disdain for individual freedoms. But Google, we hardly knew you. It's definitely time to rethink that Gmail account and demand some safeguards from a potentially dangerous company. Perhaps we, too, need to heed the Tibetan cybercafe warning: "Do not use Internet for any political or unintelligent purposes."

Frida Ghitis is a former CNN producer and correspondent. She wrote this commentary for the Hartford Courant.