I think it is mostly lingual - write in the native tongue and all that.

Yeah and some are geographical too - there used to be Polish team but now it's Polish-Czech-Slovak-Hungarian. Polish, Czech and Slovak are mutually quite understandable. Hungarians are traditionally our good friends but their language is from Mars so we have to resort to English quite often.
Borut, and you're part of another 'multilingual' team too... yeah I'm there as well