My take so far...
Arr is curretly non factioned. Some of us engage in pking but do do so in an honorable fashion. We respect the new tag and leave them alone.
SCUM(facs)/NBT(non facs) used to be allied with Arr but we fight now. We usually target sl over each other and do not share com systems. SCUM has solid numbers and seem to have more training up. A few of our former members defected to them and there are friendships but SCUM most definately is it's own set of players now. Our champs and farmers are no more safe from them than anyone else. I usually will not engage tem if they are engaged with known shard douches (see paragraph below). IMO we have "respected enemy status" with them but no rules regarding looting etc.
FSP/Shadowlords faction- appear to be mass recruiting, are good for gen chat meltdowns, and also have some former Arr members ad allys who defected to the cause of defecation. they have good numbers, quite a few solid pvpers, and generally represent the worst the pvp community has to offer. There are a couple of notable exceptions to general Shadowlord douchebaggery who were former Arr members (GOD and Satan).
Gil/i4ni/tnt I think are allied with some players in TB faction. I rarely see any of them but know most of them from way back and are a decent group of players. I wll fight these players because they are not aligned with us but would be sure to take the uptmost care not to ruin thier game experience in any way.
This, of course, is just my take on things from what I see going on day to day.
P.S. good thread..hopefully the pop continues to increase to the point that it gets harder and harder to keep track of thigns lol.