If you set opguard on, only your AOp/SOps can be opped in your room. Anyone else that is opped will automatically be deopped by services. People can still be voiced. Network operators can be opped in rooms with opguard on. This way if problems do come up, opers can be invited in to help out and be opped in the room.
Example:
/msg chanserv set #spiderslair opguard on
This can be a useful security measure. Most rooms will not have a problem with allowing their AOPs to op whomever they trust, that is to mode them +o in the room. But use this if you are having problems with people opping inappropriately or want to strictly control who has ops. This also affects the SOPs and founder, but they could always add someone to the AOP list at any time they wanted to op the person. The downside to opguard is that if the room runs into problems or runs low on ops, then the current ops cannot op more people to help them out, although they can still have network operators assist them.