• The Wall Street Journal, Thursday, May 19, 2011 11:52 AM

Respectively, "Like" and "Tweet" buttons notify Facebook and Twitter that a user has visited a particular Web site even when they don't actually click on the buttons, according to a study done for The Wall Street Journal. "For this to work, a person only needs to have logged into Facebook or Twitter once in the past month," The Journal reports. "The sites will continue to collect browsing data, even if the person closes their browser or turns off their computers, until that person explicitly logs out of their Facebook or Twitter accounts."

Facebook, Twitter, Google and other social widget-makers say they don't use browsing data generated by the widgets to track users, while Facebook says it only uses the data for advertising purposes when a user clicks on a widget to share content with friends. Still, "Revelations about the social widgets come amid growing concern about the privacy of Internet and smartphone users," The Journal writes. In particular, members of Congress have introduced at least five privacy-related bills this year, including three that aim to create a mechanism that would let users disable tracking.

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