I would think it would be wisest to put your OPC in your home and to lock the doors, but I suppose it depends on what you want your OPC to do for you and if you have the choice at the time you're logging off to put them in that ideal place.

As for running in OPC mode while logged in, don't count on that. I don't see it happening given what's been said. But we should be able to create, run and test these scripts in an offline mode so you can deploy them with some degree of confidence in the world.

I think it would pretty much kill the idea of OPC:s if players lock the PC:s inside before logout. They are supposed to keep on living as OPC:s to keep the environment lively. But then again it is not good if they then start doing thing the player does not approve.

There will still be many NPCs so it won't be a dead world in the absence of OPCs. I see the OPC as solving the problem where players can logout to escape consequence or otherwise stymie progression of the game/story/etc.

Still, I don't think every player will lock their PC inside a room in a house before they logout. Some won't be able to find a room when they need to logout. Others will be stranded somewhere. And still others may want to do things that cannot be done inside a room in a house. So many people will have to weigh the risk of "something" happening against the benefit of being productive in-game for 12+ hours via OPC slavery.