An excuse you can use after Facebook creeping and getting caught. It always works, though the suspicious individual will likely remain skeptical.
Sarah: "Are you creeping on me? How did you know I commented on that picture?"
Derek: "No, it was in the news feed!"
Sally: "Like OMG he is the best BF ever!"
Jared: "You mean Braun?"
Sally: "How did you know he was my BF?! I haven't changed my relationship status yet!!!!"
Jared: "It's been in the news feed."