when the Chrome .deb is installed one of the things it does is add a repository to your system -- remove that repository and it will not longer update.
A few package do that but, to my mind, it's almost worse that they do because they're altering a system file when all you want is a browser. Yes it's convenient but, to me at least, it almost seems sneaky -- I'd rather Google publish repositories as Oracle do for VirtualBox, for example. But that's just my opinion.

They used to publish the repo on their website some time ago, which is where I originally got Chrome from. I also agree that the package shouldn't add it's own source entry either. Seems like M$ behavior to me.

Opera also asks if you want to add their repository to your sources list when you download and install their .deb file.

At least that was so last time I tried Opera.

Ah, I thought Opera was different but forgot how. It asks, which is a good middle-ground if you ask me.