yahoo implemented it first and google decided they must have it too.
try sending them feedback there: http://www.google.com/contact
i don't think they'll remove it unless they get enough complaints
you can use google.co.uk or google.ca because thye don't have that feature yet, i believe in the end they'll add it to all their locales.
another way to override it(though not practical): if you have noscript, add google.com.. this should kill-off the completion but all google services will suffer too and if you have googlemail; you will not be able to use most of its' features.