Adobe Flash for web developers can be a pain in the ass. It is very hard to work with and there is almost no purpose anymore. Anything you could do with flash has been implemented in to the new HTML5 that we should all be learning. Flash is also not a very lightweight language. HTML5 is very lightweight and much faster than Flash. If you completely forgot about all of that Flash still does not work on mobile devices which many people do half their web browsing on.