[rlpb]

> People are not used to a search area that looks up local AND internet resources.

This is the crux of the matter. I would argue that they are used to this. Ordinary users aren't aware where they are conducting a search at all. They just expect the computer to figure out and do what they mean. The distinction between the Internet and local storage is already being lost on them (examples: Dropbox, Google Drive). The fact that so many users put URLs in a Google search box is a perfect example of this phenomenon.

The set of users who do understand the difference are capable of directing their computer more specifically. The default does not matter for them.

Ubuntu is supposed to be usable by everyone. This is (I assume) why the default is the way round that it is.

> the lack of obvious warnings

Have you looked? There is a warning on the same screen as the box, complete with a link to a privacy policy. Or are you saying that this isn't enough?