One of my complaints about a Mac was always that the Google search box in Safari searched google.com by default, and there was no way of changing it. And now it searches google.co.uk...
You are quite correct, sir. I have always been amazed that this wasn't easily changed in the preferences. I suspect it only happened yesterday - that's when I noticed it, anyway.
I think this must be a google cookie thing - I use Mozilla and if I type in google.com, it flips to google.co.uk... Location-based cookie from IP I think.