Very true, but eventually all trademark cases are decided in FEDERAL COURT which has the established practice of ignoring common law and deciding the case based on Federal trademark law. Common law may help you in state court or your local county circuit but if the "hi-jacker" trademarks the name and files suit in Federal court (which trademark plaintiffs always do) you will lose, guaranteed. You don't know if they will issue a TM until you file and get an answer one way or the other. So ignore the advice you were given and file for one. It's not that expensive of a filing fee and can be done by online services for a nominal service charge . I would attempt trademarking the name for carpet cleaning. In other words don't go too broad in your application and try trademarking it for cleaning services, cleaning & restoration services, cleaning products etc. Sometimes people get carried away and their trademark is turned down for that reason.
Always remember, Federal law trumps state & local law . Common law is (unfortunately for you in this issue) nearly a joke of an argument to assert in trademark litigation.
Perfect example of Federal law conflicting with State law: The state laws passed making Obama care illegal in that particular State, a worthless political move with zero legal merit. That also is very unfortunate in my opinion.
I really hope this works out for you. I know you have worked hard establishing your business and these little annoying issues no one needs especially if he does Groupon. That could soil the name to the point that you would be better off finding another name. Best of luck.
