I don't think it's fair to say that the Hulu developers "picked" flash. The number of technologies suitable for displaying video on the web in a reasonable way (pre-html5) is extremely limited, flash is pretty much the only game in town.  Vimeo, youtube, break, etc, they all use flash. Now HTML5 is at least a reasonable alternative for a small fraction of web users but still Flash is the only reasonable option for video on the web today.