Anthony Elonis was put in prison in 2010 for making threats on Facebook targeted at his wife, an FBI agent, and suggesting that he might shoot children in an elementary school. As courts decide what online content crosses the line of criminal activity, the Supreme Court will revisit Elonis' case.
Background:
Supreme Court To Decide When A Facebook Death Threat Should Send You To Prison [Forbes]
Supreme Court to hear case on Facebook threats [USA Today]