If you are managing a network connected to the internet with limited bandwidth, sometimes it makes sense to block unwanted traffic. To corporate or academic networks, blocking audio and video files are not uncommon. If you are like me, I also block Microsoft executable files. :)
Here's a quick tutorial on how to do content filtering using Squid on Linux.
Similarly, you can block users from accessing specific sites, such as those NSFW (not safe for work) websites, also using squid.
Whilst some think that this is too extreme, but believe me, sometimes you have to do it just to preserve your bandwidth.