I saved an alliance today. A level 44 in Un'goro was dying to a pterrordax and I saved him while farming thorium for Cataclysm.
My husband's best friend would say to kill them all, they deserve it, then shake his head at my live and let live philosophy. His thing is that he's a paladin and leveled up before that little OP spike in early Wrath, so he hates PVP as much as I do, except that he never survives a world fight and I sometimes do.
I've killed maybe 3 or 4 lowbies in my time, but for the most part I'll help them if they don't meet any of my auto-gank criteria.
The thing is, I want a good reputation. I told husband "I realize that they have horrible people, but they're not all bad, and I want to be the better person."
Now that I have pretty bird, I'm a little more visible on my server, a little more memorable, and I frankly don't want a rep as a huge ganking b-word.
So I try to be nice, because being a good person (and being seen as a good person) matters to me.
Just, you know . . . don't get between me and a rich thorium node.