When is Facebook NOT messing with you?

LONDON, ENGLAND - MARCH 25:  In this photo illustration the Social networking site Facebook is displayed on a laptop screen on March 25, 2009 in London, England. The British government has made proposals which would force Social networking websites such as Facebook to pass on details of users, friends and contacts to help fight terrorism.  (Photo by Dan Kitwood/Getty Images)

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    When is Facebook NOT messing with you?

A recent experiment was a more intrusive version of what Facebook does every time you visit your page, says one expert.