Tom Dale, Senior Staff Software Engineer at LinkedIn and co-creator of Ember.js, in a post where he argues that compilers are the new web frameworks:
Native code tends to have the luxury of not really caring about file size—a small 40MB iOS app would get you laughed out of the room on the web. And AAA game titles accept minutes-long load times in exchange for consistent 60fps performance, but I shudder to think what a 30 second load time would do to the conversion rate of your e-commerce site, 60fps or not.
While I agree with most of his post, that compilers are becoming increasingly more a part of a web developers workflow and thus becoming very important to learn, this particular bit isn't a fair one-to-one comparison in my opinion.
Web apps do not need to pre-load every single asset onto the device prior to running. If you were to weigh a fully native app next to its counterpart web app* you'd likely get a very similar result. It is just that a native app is downloaded mostly all at once and a web app can be loaded as needed.
But his point remains, more and more web apps are looking more like native apps. They are compiled, loaded, and completely obfuscated from the source code they originally started out at. I'm not sure if I feel this is good or bad for the web. But I do know that the barrier to entry in web development is higher than ever.
* Most web apps that have a direct counterpart on a mobile platform share lots, if not all, code these days so these comparisons are getting tougher and tougher to do fairly.