The problems start to happen when buisnesses adopt this en masse. Expect all banks to implement this for example. You can use Firefox all you want, but then you won't be able to do online banking.
Standards are really fucking important to help people stay functional in a society. This is one area that the ANCAP mindset just gets it totally wrong, unless you like the idea of being a hermit.
Anyway, we are already seeing some websites basically reject browsers like Firefox because they basically give the consumer too much protection and freedom. Arguably we've seen this before, but this may be a new tier of corporate lockout of open standards as consumer protection gets thrown in the trash. Thanks America.