...is when search engines (like Google, but also MSN) "automatically" sense what language I want to use. I live in Italy, therefore Google thinks I want results in Italian, or from Italian web pages. Well, that's NOT true. I want results and pages in English (like I want to type on an English keyboard and I also want my OS and programs to be in English). Especially if I type google.com instead of google.it. Also, when I search for development-related answers, as a result of this behaviour, I get really poor search result.

Speaking of translations: one of the worst things I have ever seen? Compiler errors (C++) translated into Italian. Even worse, VBA keywords used to be translated into Italian in some old release of Office. THAT was really crazy! :)