This was in an article on CNET.
"It's amazing what people have done with HTML, which was never intended to do rich Internet applications. And Flash was originally created for lightweight animation--literally for Mickey Mouse on the Web," said Brad Becker, who as group product manager for rich client platforms at Microsoft helps oversee Silverlight. "But these technologies were designed for something else, and people are really hacking them to do more."
In my opinion, there is a big difference between how AJAX has be built on top of technologies that weren't meant for application development and how Flash was really rewritten to create a platform intended for application development. I don't consider what is being done with Flex and Flash as "hacking them to do more"