My advice Vinyl is, if a mod or admin isn't on or there is only one on with a lot of players, start demoing. Having them in case something happens is always great. If computer space is an issue just erase the latest one as it probably won't be needed if nothing happened. CS:S has quite a lot of mod and admins (most generally inactive but there nonetheless), even then most of us are young adults dealing with school and work so we can't be on all the time (God knows I try :p). So if you notice a distinct lack of rule enforcement and an increase of rule breaking, break out a demo and give it to a high-up or post to forums. It's gonna be your best bet.
Cheers.