Well, I would say Flash's inability to perform well on mobile was the killer-blow but even before that flash was the only thing that caused blue-screen on my Win7 box... and it's always the thing that makes may laptop's fan go into warp-drive... and on linux, Flash kept claiming the whole sound-system and I'd have to close the browser to get sound out of any other app(but that may have been a linux issue more than Flash. Just interesting that Flash was the only audio-enabled thing that would cause it.) Flash was great, certainly better than COM object that embedded WindowsMediaPlayer into your browser(IE only). I was a major[1] Flash lover at one time, but it's really past its expiration date at this point. We're just waiting for solid & frozen'ish HTML5,<video> and <audio> tag RFC specs and to agree on a non-patent-landmine-covered decoders for all significant browsers to support.
Then maybe someway to "compile" javascript so websites that do flashgames(Nintendo's Japanese website is big on this) can keep doing it with HTML5+js without worrying that it's super-easy to have their content "borrowed" and re-hosted somewhere else.
Note, there are ways to make a Flash game(swf) not work outside of a given domain that would be at least semi-difficult to remove since it generally follows the same-origin rules of XMLHttpRequest. If you test for that in your actionscript, export-to-swf with obfuscation enabled and make sure the string is obfuscated so it can't be found in a hex-editor even if the export-obfuscation was reversed, a flash game hosted at http://www.nintendo.co.jp/ will not run anywhere else and it'd be kinda difficult to alter that behavior.
