I believe you have to be a resident citizen to buy them. You would also ensure that you dont' end up owning a domain that has a patented .com - lest you regret losing it under the legal system. To answer your question - does anyone buy them, Yes sir. .us is just as popular as any other TLD. Cheers, GS
one thing worth mentioning is that NeuStar, whom operates the .US gTLD, does not permit private whois data. You will notice places like godaddy do not offer it for .US domains.
.US is quite popular now!! and its easy to register i do own a .us domain Hyipforums.us and it works as any other domain! and godaddy do register .us domains, if i am not wrong!
GoDaddy does register .us domain nams. I own a couple dieting .us names that are currently registered with GoDaddy: Pudgy .us UnFit .us Kerb.us So they do register .us names. You do have to live in the United States and you cannot have private registration. I think that because of those two conditions there are fewer .us investors but the end users are there and the names are doing decent on the market. Just make sure it is a good name.
I've got one .us domain, travelsafe.us Not a huge fan of the extension, but there are definitely a large number of people who trade them.