Most people also said they are very concerned about advertisers targeting kids with personalized ads, companies holding onto data even after they don't need it and online data being used to prevent someone from getting a job or a loan.
The study found 44 percent of consumers are very concerned about advertisers tracking their online activities and targeting them with ads. And 42 percent of the respondents said they are very concerned that privacy policies are too long and complicated.
Consumers Union, the advocacy arm of Consumer Reports, submitted the survey results to the National Telecommunications and Information Administration (NTIA), a Commerce Department agency that is leading discussions between consumer advocates and Web companies about how to better protect consumers' privacy.
"A lot of people are seriously worried about how their personal information is being exploited," said Ioana Rusu, regulatory counsel for Consumers Union. "Your personal data ought to be treated with respect, and you ought to have more of a say in how it’s used.”
In February, the White House announced the "Privacy Bill of Rights" — a statement of principles about how Web companies should handle user data. The Federal Trade Commission released its own report on online privacy last month and urged Congress to enact certain privacy protections into law.