Trademarks are registered that cover certain things and are NOT just a general trademark for a name or word. You can register and use domains that have a word or name in them that are Trademarks in something that is not related to what you are using the domain for.
As an example, if you register FordParts.xxx and you would be selling auto parts then that would be a trademark violation. However if you registered the same name and used it to sell parts for Ford telescopes (Made up) then that would be ok because Ford Motor Company doesn't have a Trademark for telescopes or parts for them.
It all depends on the use of the name. You also need to make sure that you did ot register the domain in "Bad Faith" meaning that you registered it with the intention of violating a trademark or using the name to profit from a trademark holders TM.
In general though it is a good idea to stay away from domains that have a trademark in them because you can sometimes get a lot of cease and desist notices by scammers and even the TM holder.
I have been in the domain business since the 90's and have seen all kinds of things happen with TM's so I always like to stay away from them just to avoid the BS
If you are unsure of what a TM is for then you can check to see what the TM is for at the link at the bottom for US trademarks or if you want to check your/other countries TM's you can Google and usually find the site to check them on easily enough.
http://tmsearch.uspto.gov/bin/gate.exe?f=tess&state=4803:p7to13.1.1
P.S. Buying a domain and parking it to earn parking revenue can be seen as profiting from a TM holders TM and can get the name taken away through a UDRP or even slapped with legal actions. It usually doesn't happen but it can and does.
I used to own justtwitter.com and some others as well, never had a problem.
