I have seen a few arguements here that are both for and against PvP. I think some people are afraid of griefing/newbie type killing, and PvPers don't want some "okay if you want to PvP you have to go here to this arena and specific PvP zones".
There are ways to protect newbs and still provide a dangerous PvP FFA type world. One way is that PvP is disabled until a certain level so newbs can't create their character and be killed the second they pop in world. This allows player to get used to the world.
Next, one would assume that towns will be relatively safe with some form of guards and frontier law. When you leave towns and the further you get out in the wastes, the deadlier it becomes. Really, I think the whole fear of creating a character and instantly being killed is silly, as it is extremely easy to make sure that doesn't happen.
As far as loot goes, and full loot, limited loot..well, I would assume again there will be a weight limit on how much we can carry. However, loot depends, imo, on how rare loot actually is. If gear is hard to replace, full loot can be a pain. Generally, loot is hard to come by early, easy to get later. As long as their isn't epic items, loot doesn't seem like much of a big deal, but I'm not opposed to limited looting.
What I am more in favor of is acquiring a trophy. A scalp or ear or both from a kill. Maybe even skin them.
Full consent for PvP makes no sense to me in a wasteland. I just can't picture a slaver or raider asking consent for anything.
Another idea tossed around is faction based PvP. That is fine, however, I think certain factions, slavers/raiders, would be two factions who could attack within their faction without penalty. Again, I can't picture either of those groups agreeing to a friendly duel. I'm not suggesting a ffa in a slaver town, but if I am a slaver, and another slaver ticks me off, I should be able to follow him outside of town and attempt to dispose of him, with no faction penalty, not challenge him to a duel at dawn.
A couple other things that have ticked people off, is equiping a low level character with powerful gear, and this character becomes a lowbie killing machine. This only happens if their is level restricted pvp, and it can be eliminated if items are skill or level restricted.
With that said, I can care less if I can only loot caps, ammo, food and water, as long as I can take a trophy such as a scalp, I would be a very happy gamer.
One last thing. I hope there are more interesting ways to kill another player than just point and click. For example, giving them bad drugs, poisoning food/drink, traps, etc. that could be detected or not depending on a skill check.