So I just had the weirdest thing happen.. I'm just running around in Ashenvale with a lvl27 belf mage, doing quests and whatnot, then I casualy passed a lvl80 space goat shaman.. And this is where the weirdness starts - so I pass the guy, I see him targeting me but at this point he doesn't kill me, so I'm like "Whew that'll save me a few secs of ghost running..", but then, after I'm like 30-ish yards away from him I see him stop, at this point I'm guessing he was deciding if not killing me was a bad idea, and I guess he was like "Screw that horde dude, I got PKed by hordes so now I should do the same", or something of the like, and then he chased me down, didn't even Shock me or something, just caught up with me and slaped me with an axe. So yeah, fun times for everyone.
TL;DR - PKs suck. Be a good guy and leave the lowbies alone, jerks.. :P

