I've always wondered that, the social interaction aspect. How much is programed in the game? In real life if someone walked up to you and tossed a vial of something that made you sick, you'd be really ticked off. I doubt you would be nice and invite them over for coffee, or for me, tea (love the smell, can't stand the taste of coffee).
How does the game act? I know that mailpersons, police, firefighters are NPC; can they be friends of townies?
Could they (or a townie) react to actions of the player's sim? Revenge is sweet type of aspect? I can think of a lot of nasty elixers I could toss at some of the sims in SV. Can't remember his name (Jared Fro ?), Connor's brother, and the kid with the spiked hair; VJ I think is his name, or his brother's.
I've found my sim's bills on the ground; I thought it would have to do with if you didn't pay it that day, when the mail arrived the next day it was tossed out of the mailbox.