There are numerous pitfalls that may arise whenever any other party is allowed to use your mark.
Powersquid is registered with the U.S. Trademark Office for electrical extension cord sets having multiple outlets. REGISTERED TRADEMARK 3,099,238
A trademark can be used to help in protecting the "commercial embodiment" of a patented item.
While it is not illegal to allow (i.e., license) someone else to use your mark, there are numerous pitfalls that may arise whenever any other party is allowed to use your mark.
Unless you have a nationally recognized, famous mark that could raise significant revenue from licensing other goods and services to use the mark, the best approach is to avoid allowing any other party to use your mark. In any event if you believe the circumstances may merit further consideration, seek advice from an experienced trademark attorney.