A question most web companies in the US probably don't have to worry aboutbut one almost all British ones must is, do we write our pages in British English or American English?
Building applications I've had more than a few conversations with @Simon_Chapman about it - we want to appeal to an international audience so the framework for internationalisation is already in place. Java web applications make it pretty easy anyway, we just take the time to build the application, even if we're starting with a single language version, as a properly internationalised application.
Jakob Nielsen talks about it here as well and I agree with most of what he says, which basically comes down to the fact that it's all about the users. If you're targeting a British audience than you should write for them, if you're targeting an American audience then you should write for them. If you're targeting an international audience you should translate - it really isn't that difficult.