Digging through trash while a villager can see you
Garbage cans can be useful, but rummaging through one near most villagers costs friendship.
Why it hurts
If a villager other than Linus catches you searching a garbage can, you lose friendship with that villager. Linus is the exception and actually reacts positively.
Do this instead
Check trash cans when the street is clear, or do it early and late when NPC paths are easier to predict. If someone is nearby, keep walking.