Well I see your point, but what if my game was multiplayer? Just write the files in a binary format and hope for the best?
There is not much you can do against a determined attacker. Whatever is on his computer can be read and modified by design. You cannot prevent that short of keeping assets away from the user and rendering the game on dedicated servers, delivering the results via the internet (see OnLive) which is really overkill. And even then he might still be able to recover the assets to some extent (e.g. stare at a wall and screenshot the texture on his computer). It's just not a 100% solvable problem in practice.
To be honest, just packing all your assets in a zip file and renaming the extension will discourage 99.9% of people out there from snooping into your assets. That's probably good enough unless you have an AAA game in the works.
Basically, you are attempting to solve the DRM problem, which in short is "how do I make sure someone cannot copy X while still having access to it" which is fundamentally flawed in the abstract computer realm, because while it is difficult to replicate a physical object, all information in the form of bits (i.e. everything on a computer) can by definition be copied.
Edited by Bacterius, 03 January 2013 - 09:07 AM.