It is a common belief that obtaining a domain name insulates the owner from trademark infringement lawsuits. This is not true. For instance, acquiring AOL.net does not shield the owner from a trademark infringement lawsuit brought by American Online, as AOL is trademarked. In essence, federal trademark law trumps any granting of a domain name by a local registrar.
On the other hand, registering for a domain name does not automatically give the registrant a protected trademark in the name. Domain names can contain and themselves be trademarked, but most domain names are not. Even if the domain name is intended to be used in commerce, a trademark is not spontaneously generated from that commercialization. So a “race” to a domain name between two competitors does not grant the winner a trademark. The winner simply acquires the right to use the domain name.
Some confusion can arise from the fact that both domain names and trademarks need to be “registered.” However, obtaining a domain name from a registrar is completely different from registering a trademark with the United State Patent and Trademark Office. The former is leased from a private (or quasi-governmental) entity with a specific end date; the latter is registered with the USPTO and can exist forever as long as the owner continually defends it against infringement.
Trademarking a domain name is possible, but it requires an affirmative action beyond obtaining the name from a registrar. The name should be registered with the USPTO and approved for use in commerce. Though non-registered trademarks can be defended against infringement if in use, the protection is weaker and the case is much harder to make. If one wants to trademark a domain name, he should speak with a lawyer and seek official registration of the mark.
 Brookfield Communications, Inc. v. West Coast Entertainment Corp., 174 F.3d 1036, 1052 (9th Cir.1999).
 See this information from the USPTO: http://www.uspto.gov/sites/default/files/trademarks/basics/BasicFacts.pdf