I've seen a lot of discussion about hostile NPC's so I thought i'd chime in.
I could see having an option to turn on or off something in the line of BANDIT CAMPS randomly generated on world creation. They could also have an adjustable amount of NPC's, patrol/raid range around their camps with difficulty settings. The camps would be a bonanza of high tier loot to give reason to raid them. I think this would be a good way to satisfy both types of gamers as well as a good scenario that fits into the game. As well as giving solo players the ability to raid them as well by changing the difficulty settings.