A survey released just before important government hearings on Web privacy suggests computer users are extremely vulnerable to cyberspace spying and other personal intrusions by Internet businesses.

The results could help frame one of the most fundamental debates in the evolution of the Internet as a commercial marketplace: whether the industry can police itself or the government must step in to protect millions of personal-computer users.

Starting Tuesday, the Federal Trade Commission will hold unusually broad hearings in response to complaints by privacy advocates that personal information is gathered and used by online operators without user consent or knowledge.

The Electronic Privacy Information Center, a nonprofit consumer group participating in the talks, released its survey to The Associated Press Sunday.

It found that of the Internet’s 100 most popular Web sites, about half collect personal information from users who click on their sites or through mailing lists and other means.