Allison over at O'Reilly Radar wrote a little note to Google for the international feature.
By Allison Randal
I applaud the enlightened international perspective that led you to provide your site in multiple languages and to detect a user's country and language preferences by their IP address. You'd be surprised how much French I remember from studying it as a child, and how much Dutch I can read as a result of studying Afrikaans the past 3 months. However, perhaps you should consider providing an option to change languages, or set a language preference, so your users aren't all forced to be so linguistically nimble when traveling. If there is such an option, I haven't been able to find it yet while navigating my account preferences in Dutch. I'm curious to experience Google Docs & Spreadsheets in Japanese, but maybe not that curious.
I post this as proof. "Google guesses your language based on your IP address." and you doubted me!