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The US domains have been in place for quite a while (I had 50 at one time, gave a few away) and were set up in a way that made them best used to point to geographic places and governmental entities. It's interesting to note that even these entities have abandoned the .us domain for a .com in many cases. IMO, it will take a long time before .us is recognized as anyting but an oddity within the country. However, it may play very well in international markets where the various regional domains are very familiar to the users.