by aswynn81 » Mon Oct 10, 2011 10:48 am
You cannot use someone else's existing trademark, or anything similar, to market your own goods or services in any related field, whether or not their trademark is registered (under US state and federal law).
Unlike what someone else has said, it is NOT a violation to simply reference someone else's trademark, such as using the name in the title of a review. For instance, I could say, "McDonalds Restaurants Golden Arches Somewhat Tarnished in Zoning Fray", and it would not violate anyone's trademarks and there would be no merit to any legal action brought to prevent me from publishing the article anywhere.
In your case, if the existing trademark is related to anything you're selling, you're looking for trouble, especially if they have gone to the trouble and expense of having it registered federally. On the other hand, if their trademark is not particularly strong (i.e., it means lots of OTHER things too), you could argue that they have not acquired the right to stop you, even if their trademark is already registered. Trademark examiners sometimes make mistakes, and sometimes applicants misstate the evidence of the strength of their brand.