A dirty little secret known to those of us who do troubleshooting work is that Adobe's Flash plug-in has long been one of the least well-behaved pieces of "required" software for users. Users insist on having it so they can use content spread far and wide on the web, but it has never been particularly stable, it's a tremendous resource hog (hear the fans spin up on your laptop while you're browsing the web and you can be sure you just landed on a site heavily using Flash content) and there are continued issues with security vulnerabilities. However, it's a deeply entrenched technology, used for everything from coding websites to online games and videos, etc.
When Apple was teetering on the edge of survival it needed to keep Adobe happy, and so Macs shipped with the Flash plug-in installed for many years. Then Apple quietly stopped including it. Finally, with the advent of iOS, the iPhone and iPad Steve Jobs announced in April of 2010 that there would be no Flash support in iOS, and Flash would not be allowed on the platform. HTML 5 would be the only acceptable method of delivering the rich media content that Flash had had a lock on. Jobs went so far as to publish his reasoning in an open letter, Thoughts on Flash.
Jobs' reasoning was sound. On a laptop Flash could kill a battery in no time, machines became unstable when running badly coded Flash content and Flash left a gaping hole in the otherwise exemplary security of iOS. By keeping Flash off iOS Jobs was ensuring that users of iOS devices would get an optimal iOS experience without the worries introduced by Flash.
Adobe struggled to deliver a satisfactory user experience with Flash on Windows Mobile and Android, but the reasoning behind Jobs' decision had been sound and Adobe was never able to deliver on its promise to mobile developers.
Adobe makes a lot of money from Flash and it's very popular with developers, and thus began a PR war waged in the press, on blogs and in snarky commentary from Adobe's representatives. But the time when Adobe could call the tune had ended and the utter dominance of iOS in the mobile space and Apple in the tech world meant the end for Flash.
Many inside the industry had realized that Adobe had lost the battle from the moment Flash had been denied a presence in iOS. iOS is tremendously dominant now, already 10% of all mobile phone sales are iPhones and the percentage of smart phones is much higher.
Today Adobe quietly alerted developers that finally it too agreed that HTML 5 was the correct course and that development on the Flash Player plug-in for mobile devices would cease. Couple that with yesterday's announcement that Adobe would lay off 10% of its workforce and Adobe looks to be in a tough place.