a mod has to be reliable, make tough decisions (people may like or not) which sometimes have to be made quickly and he needs to have a certain level of maturity. also very important i believe is that a mod has to set an example for the members.
(what would you do if you joined a forum were mods would stuff the place with spam? you´d be doin the same thing, believe me)
btw, im not sayin Z doesnt have those
im just stating what i believe are the qualities of a good mod