Common law trademark is usually established under the United States law when someone uses a business name, slogan or logo in commerce, even if it's yet registered. Therefore, you may decide not to pay to register a trademark since a common law trademark exists. However, the common law trademark right is limited to the geographic location where the mark is used against the federal protection customarily acquired when a mark is listed with the USPTO. Hence, unless registered, the use of a mark can be geographically limited, which hampers the ability to grow the brand. On the one hand, a person using a mark in a limited geographic location could be boxed in by another person who offensively registers a similar trademark.