Cameron Walker learned the hard way that sharing information online can have unintended consequences. in 2005, the sophomore at fisher College in Boston organized a student petition dedicated to getting a campus police guard fired and posted it on the popular college social network Facebook.com. Walker wrote that the guard "loves to antagonize student ...and needs to be eliminated." It was a poor choice of words. Another student informed school officials, who logged on and interpreted the comments as threatening, Though Walker claimed he was trying only to expose the guard's demeanor, he was expelled. He is now enrolled at another college and admits he made a serious mistake. "I was a naive 21-year-old," he say