In a recent article from the Boston Globe, an interview with the new manger of WBZ-TV in Boston stressed the importance of the stations call letters. The article talks about the connection that the local audience had to the well-known station call letters , and how the station had suffered to some degree by de-emphasizing those call letters while using other station branding. That story, to me, raises the question of whether stations have taken the necessary steps to protect their brand by protecting the use of their call letters.
Since 1983, the FCC has left disputes about the use of confusingly similar call letters to local courts. Thus, if a competitor picks a set of call letters that could confuse the public about the relationship of their station to yours, you may need to sue to stop that use. And now, when stations often keep alive formats that have been dropped by moving the formats onto Internet Radio Stations or to HD Radio subchannels, the call sign may well live on even after it has been dropped from a primary on-air station. Thus, it needs protections other than those provided by the FCC.
In 1983, the FCC stated that stations had a sufficient interest in call letters to obtain a service mark. A service mark gives the call letters the protection of Federal law, and may impose penalties on a competitor who tries to infringe on those call letters. To protect that brand, the investment of a few hundred dollars to file a service mark application may well be worth it, and something that more stations should consider.