"do the job"
Reliance on a single corporation's tools for all of your client-side web development is a horrible idea. It ends up limiting your reach, interfering with network effects of the web, and locking you into "security when we feel like it" from that one and only vendor. This is the situation with Flash. Technologies like JavaScript (which, by the way, is essentially the same language as ActionScript, the language used by Flash -- both are just ECMAScript implementations) are widely implemented and deployed, with no single-vendor reliance requirement like Flash enforces. Sure, the libraries and environments aren't quite up to the level of what Flash provides for certain tasks, but given time they easily could be, and you'd then be freed of the restrictive detriments of Flash development.
