Is Flash the best choice to make interactive content spreadable?

We have developed an authoring environment for kids and novices that allows them to create games and animations (http://scratch.mit.edu). Currently, once people upload their creations to our website, they get rendered by a Java applet. We're considering switching the player to Flash but we're weighing the pro's and con's. Would having the content as Flash make it significantly easier for our users to spread their creations via Facebook, MySpace, blogs, etc?