" People are starting to expect that "search" doesn't just mean "search locally", it also means "search on the Internet". Many of the search tools that they interact with (Chrome and IE address bars for example) default to this already."
The evidence you provide to support your assertion that is somehow people's expectation that search results will connect to internet automatically is very weak. Internet browsers may search the internet and that by itself is not very surprising but desktop interfaces in general do not connect to the internet to search things automatically by default. GNOME Shell for instance, used to provide link to wikipedia and google from the shell search interface but it did NOT search google and wikipedia by default. That would have been a surprising privacy violation.
The primary reason Canonical seems to be doing it is because of a commercial contract with Amazon. If you can point to any other OS search interface that connects to the internet by default to get search results, you might have a point. As it stands, I think this is very much a unprecedented move and not at all in line with what users expect.