I think one of the most insidious things about Photoshop is that it is a powerful, complex program. Using it is a skill. Which means that even if you think you are getting the better of Adobe by pirating their software, you are still building your own skills with their program, which is so full of features that classes can be taught about using it. In the end, that’s a win for Adobe and their proprietary software, because if you end up getting good enough to make money from that program, you will end up finding yourself in a position where you eventually pay them, or work for someone who does. This is to the detriment of any other photo editor, of course. You won’t care about how good GIMP or anything else is, much less fund it, because you won’t want to use it, because you know Photoshop.
If I had deep wallets I would love to start funding GIMP for development and rebranding. But I don’t have that kind of cash to push around :P