This comes up in just about every talk on HTML5 to general app and game developers. People reasonably want to know how their application code and content will be protected. Some points:

* The best form of protection lies outside the code. There are a million Twitter clones out there, so Twitter's value lies not in the source code. It's in the service, branding, and user base.

* You can indeed obfuscate code. It's true though that DRM is not as acceptable as Flash (which is security by obscurity anyway) to content owners. People are working on this, e.g. the various JavaScript crypto standards.

* Fortunately, the people who will outright steal your code are rarely the people you have to worry about. They usually can't innovate (though there are exceptions to be sure) and will always be following behind you.