This subject is raised alot around here, and unfortuantely many new members fail to see the significance of asking where they are from. Usually after they post a geographically sensitive question someone here will remind them that knowing where they are from would help, they get the point. I have pointed it out to new members many times, mostly they get it when explained.
There is also the language issue, people tend to be more tolerant of someones attempts at communicating if they know it is not their native tongue. The "leet" speakers I tend to ignore. Save it for your cellphone, or crackberry, LOL. ( that's a R.I.M. device, inside joke maybe? )
Maybe if there was some sort of explaination given beside the field on the sign-up form it would help? Along with making it mandatory.
Unfortunately some people will always choose to put some useless nonsense in the field.