I would like to know the answer as well! We have multiple conference rooms
setup on the exchange server, for use as resources, and they keep getting
double booked.

Why does the exchange server allow this? There should be an information
window informing the meeting planner the resource will be double booked or
already booked.  I have setup meetings and the resource calendar was open and
available but in reality, the resource was already booked with another
meeting. This other meeting wasn't visible on the resource calendar. Both
meetings were setup properly with the conference room listed as a meeting
resource.

I wonder if this happens when multiple meetings are setup for the same time
for the same duration, thus, one meeting is "hidden" behind the other?

Things that make you go hmmmmm.