Ok, but obviously in this case you can check the "Don't show me this message again" checkbox and, like me, you'll have had to endure the burden of responding to this nag just once in years of using Firefox.

I may be forgetting about nags that don't allow themselves to be disabled, but if so, they're infrequent enough that they seem insignificant and obviously non-memorable.

Edit: I should add, when I had to have Chrome installed I really didn't like the fact that it updated itself automatically via a daemon process. I don't think having a constantly running background process for a browser, especially one from a giant advertising company, is a good alternative.