The simple one "for the moment", aka, in one of my server zone "The Ruined Citadel", i have different "factions".
- Forsaken Guards "the good guys",
- Innoruuk's Legions "the bad guys"
- Cazic-Thules Legions "the bad guys"
Forsaken guards will attack innoruuk and cazix-thule legion when they will see them, because killing bad guys give good guy faction and reverse.
I have also animals in the ruined citadel, i decided to not add faction to them, i find having faction like "wolf faction" there is in EQLive (Kelethin) totally stupid and not RP at all. So when newbies will attack animals and come next to guards, they wont help, yes you are ally with them, but do this mean they are your slave and will "risk" their life for an action they dont care about ? As their job "GUARD" is only to protect city, not to help you kill animals.
Well this is only my point of view, and i know this can make a loooooong topic