Federal Trademark Owners v. Prior Users
Congratulations to those of you who have a Federally registered trademark! Registration comes with many benefits. However, one of those benefits is not the exclusive right to use your trademark. If someone else has already been using the same or a confusingly similar mark in commerce prior to your use of the mark, they are called a Senior User in trademark law. The Senior User has common law trademark rights that are superior even to the owner of an incontestible Federally registered trademark. Furthermore, if someone else started using the mark in a different market area after you did, but before you obtained federal registration of your mark, they too have rights superior to yours.
Once you obtain a Federally registered trademark, you obtain the exclusive right to use that trademark IN ALL AREAS WHERE THE MARK IS NOT ALREADY IN USE. So, if you chose well and picked something nobody else is using anywhere in the U.S., you will have the exclusive right to use your mark for the goods or services you selected in your registration. But, if others were already using the mark before you obtained a registration, then you can only stop them from expanding their market into new areas.
The moral of the story is that if you are considering using any mark in your business you should consult a trademark attorney and have them do a search for potential conflicts. If you have already been using the mark for some time, at least an attorney can advise you of the potential risk factors and options you may have to enforce your mark against others.