IANAL, just a many-years radio station program director, but this makes me very aware of music performance laws and practices.
In an office or any business setting, be very aware of music copyright laws. Any use of music that is deemed a "performance" is controlled by and normally forbidden by the copyright owner, especially in a commercial context such as an office. This includes playing music over a PA or extension speakers, over a network through various receivers/clients/speakers, as music-on-hold, etc. In the news last week was a car repair shop being sued for playing music in the shop loud enough for customers to hear it -- a performance!
Doing it legally involves a license and fees from some combination of the RIAA and ASCAP and BMI and all the others who control music use, similar to the payments made by bars, discos, live performers, show producers, broadcast radio and TV, Internet radio stations -- anyone who uses music or any other copyrighted work in a public context. Anytime we hear background music in a store, restaurant or elevator, there is (or should be) a license involved. In the days when bars had massive jukeboxes, the bar owner paid a music license to allow the jukebox to "perform".
This same performance copyright restriction is why it's not legal to set up a TV for viewing in a business waiting room (or bar or any other public place) without a special license. It costs much more to sign up for DirecTV or Dish if the user's location is not a residence because the TV feed is presumed to be a performance.
The gray area is the much acclaimed but poorly-defined "for personal use" concept. It probably allows distributing music through multiple systems/speakers in a home, but it is gray because while this type of "performance" seems like "fair use" to us civilians, some of the copyright controllers seem to think otherwise, as suggested by statements during the recent RIAA lawsuit against a music file sharer.
But in an office, beyond a personal desktop player/radio used by one person, there's likely no "personal" defense. In fact, all the clever PowerPoint presentations that include pieces of hit songs or even background music could be deemed copyright violations, even though there is clearly no "entertainment" value to the bored audience.
The "solution" if there ever is one will require rewriting copyright laws to more cleanly define personal vs. commercial use. But the copyright "protectors" seem to have much more political clout than music lovers.
Based on my understanding of all of this (I've actually read the copyright laws and had various performance licenses), while I love to play my personal music collection in my personal office (iPod synched with MC), I've never been willing to feed it to anyone else, despite many requests from co-workers.