@mcc Anyway, it would seem like, at the very least, these are features that would entail a bunch of extra code (mostly the local model more than the interface to the cloud services) and therefore open a larger attack surface. If for no other reason that that, it does seem like people who have no interest should be able disable it in the interest of security.

And, to come at it from a slightly different perspective, it seems like for most new Firefox functionality the burden of proof should be on the side arguing why this couldn't/shouldn't be an extension. Perhaps there's some technical reason why not, but this *seems* like something that could be an extension.