In all seriousness, it's a liability issue, because it very well can blow very expensive surround sound headsets -- hell, probably even mediocre decent sets made for gaming. And nobody wants to spend $160 because of a joke that an admin thought was funny on a day that should have been fun.
The rickroll is fine. I found it amusing too. Just saying, it'd be beneficial to all to pipe down the volume. Less broken Turtle Beaches and/or woken up households.
Edit: Oh, right, and detrimental to hearing and all that stuffs....