Sure Disney, just like any theme park, is going to be germ-central. Disney does do just about as good a job as any park in the world at keeping it visible clean, but I mean yeah when you have 10s of thousands of people passing through a park in any given day, things are going to get a little dirty. If you start thinking about everything that everyone touches (like the joysticks on Mission Space) or things like that, you will drive yourself crazy. Ignorance is bliss sometimes
Best thing to do is to remember to thoroughly wash your hands every chance you get, but especially before eating something. As far as the Purell, I do think people (healthy people w/ no immune system issues) can get a bit carried away with it. Our hands have naturally bacteria on them that help protect us from bad bacteria. Hand sanitizers don't discriminate and kill nearly all bacteria on your hands. Some of that stuff is there for a reason!