At least when a ganger beats someone up for 'dissing him' there's a logic to bragging about it, the crime was part of a greater motivation to be feared and respected and that requires advertising. Ditto, someone forgetting to wear gloves during a robbery is guilty of "Stupidity by Oversight" and dumb things during a crime can be partially excused by a need to rush or fear, adrenaline, and anxiety clouding thought.
These are like taking an ad out in the newspaper "I, Jon Smith of 314 Pie Ave, engaged in aggravated assault yesterday afternoon on a homeless man in Grove Park, using a baseball bat in my trunk."
Though it does strike me as a great way to frame someone.
It really is.
I wonder if it's partly because in some of these cases they don't look at what they've done as a "crime" per se, but just as some annoying/quirky/dumb/funny(?) thing that happened to them and exactly the sort of thing all their social media followers would love to hear about? Part of a larger trend of social media narcissism and the filter that only makes things important/interesting based on how they affect one's self, paradoxically combined with general internet anonymity and the expectation that ones friends will agree with and be loyal to you.
Or, they could just be morons 
Personally I think they're both.
Narcissism and stupidity blended together in one big, and smelly pot.
