If you run a business, then you should definitely trademark and copyright your site as well as buy the .com, .net, .org and .us if you operate in the US. It's really a small investment, especially when you can buy bulk domains at godaddy for $7 per year. Anyways, the more domains you have, the better it is, make sure to link them all together.
.us is only for US based companies, so you only need to buy 4 extensions in order to protect yourself; .com,.net,.org and your country extension.
We own 1200 domains, but the amount of traffic generated just by link popularity due to the fact that they are all linked together more than pays the yearly $7.
just my
