I’d think this was a joke, except for the USPTO entry. Fark has lodged a trademark application for the term “Not Safe For Work.”
According to this USPTO entry, Fark wants sole rights over NSFW in the following areas:
Entertainment Services namely providing a website featuring photographic, audio, video and prose presentations featuring comedic captions regarding current events and online discussions and/or reviews of web materials of an adult nature; Entertainment services, namely, providing a web site featuring musical performances, musical videos, related film clips, photographs, and other multimedia materials; Entertainment services, namely, providing on-line reviews of photogrpahs and /or web postings of an adult nature
As Trademork points out, it might be a little difficult to protect and enforce this mark given its already widespread usage, including a range of other websites the use the term (and the NSFW abbreviation) in their title. NSFW has also become a common term used widely to the point that it even has its own Dictionary entry.