There has been many issues about Flash recently, mostly about security issues. Most of these can be seen as dangerous to computer users.
Another issue is that Flash is dated technology, as it's prone to crashing and making computers lag badly.
Al-thought, this may kill off any old sites or games that used flash, but the sites themselves may be hacked nowadays, anyways.
I'm kinda sad to see Flash die out (not even lying). As I tend to work on games with Flash. Dunno where to go next. HTML5, maybe?