My Twitter phone code (for posting tweets via mobile) stopped working a while ago, and I only just now got around to checking my settings on Twitter to see why. Turns out that, according to Twitter, I don't live in Israel.
Which would be news to Orange Israel (Partner Communications), my mobile carrier. Actually, according to Twitter, turns out that Israel doesn't exist. Here are the countries that they recognize and the short "tweet" codes that they provide for each country.
Letter to Twitter customer support sent, but they sure take pains to hide their contact form.