Should I trademark my domain name?
If you place any value on the name the answer is yes! If you do business across state lines yes again!
You make an investment - not only in the website itself - but also in the strength of, and notoriety of, your domain name. You spend days or weeks building reciprocal links or sub-contracting this work to a link building firm. And, perhaps you have your domain name printed on business cards, stationary even purchase print, radio or television adds to promote it.
Finally your investment is made, your website is successful, your domain name is widely publicized -- and now someone or some company contests your use of a name that they already had trademarked. If their claim is valid, and they are successful, you will be required to stop using the domain name.
While you may be able to move your website to a new domain name. And, perhaps the cost to change titles and related text is not excessive. Your total investment -- promoting your domain name will be lost!
Lawyers specializing in trademark law can assist you in registering a trademark. Typical cost is about $2,000 for one class of goods or services.
You can also find information about filing a request yourself at the US governments patent and trademark website: http://www.uspto.gov/teas/