From posts by residents of Oakland, California, to NextDoor and Glenfriends, two online social networks for neighbors.

Silver Dodge Caravan, two Latino male occupants, not particularly young. When I took a long look at them, they consulted with one another and headed off. This is historically the week people come to take your Christmas presents.

One African-American man claiming to be my neighbor just rang my doorbell. He wanted to know if I had a chain to move a car. He did NOT look nor sound like any neighbor I know.

My houseguest saw a strange person early Friday morning.…