Now that I have three Twitter accounts, I have to say I am very grateful that the 140 character limit is indeed a 140 character limit, and not a 140 byte limit. While that makes no difference for ASCII people, and only a tiny difference in the German language (umlauts), this is great for Chinese or Japanese tweets. For those, every character takes three bytes, but still counts as just a single character. In languages with such a rich "alphabet", you can say so much more in the short space of a tweet.