some times, most times, context is king

Twitter joke trial: Paul Chambers wins high court challenge to conviction

Accountant says he feels 'relieved and vindicated' as court rules his joke tweet about blowing up an airport was not menacing

http://www.guardian.co.uk/law/2012/jul/27/twitter-joke-trial-high-court

vs

University of Kentucky student arrested for emailing a picture of the Joker

http://www.kentucky.com/2012/07/26/2271633/university-of-kentucky-student.html