There's a fine line in play here. Websites are opt-in, as are OSes, but I don't think many people think of Firefox as 'Ubuntu Firefox', and rightfully don't expect that their OS is going to tamper with the expected behavior of known, third party programs. For the normal user[1], this is a 'browser lock-in' that seems worse than what everyone got mad at Microsoft for.
[1] By normal user, I mean the non-Linux-guru type that wouldn't think to try all the nonobvious workarounds. This clearly is no problem to the 'You only get to use Linux if you submit patches' crowd, but should be a big problem for roughly every other open source free software crowd.
[1] By normal user, I mean the non-Linux-guru type that wouldn't think to try all the nonobvious workarounds. This clearly is no problem to the 'You only get to use Linux if you submit patches' crowd, but should be a big problem for roughly every other open source free software crowd.