It protected against a weird javascript edge case in the distant past and against flash injection in the past. See also https://stackoverflow.com/questions/153

It protected against a weird javascript edge case in the distant past and against flash injection in the past. See also https://stackoverflow.com/questions/15306636/why-do-facebooks-jsonp-callbacks-start-with https://stackoverflow.com/questions/15306636/why-do-facebook...