Repo thing is not that common here, because a lot of people don't live over their income level. And theft is not that widespread too. I'm not even afraid of leaving my helmet unlocked in most supermarket parking lots.
I have confronted a guy who sat on a bike that clearly was not his. Some backpacker with a friend took photos on every bike they saw. I personally wouldn't mind that much if someone takes a picture with my bike. But I'm afraid they will scratch the bike or move it and don't put the kickstand back correctly. With my previous bike I've had this happen once. I came to my bike, and kickstand was pointing backwards. If the bike was not in gear, it would have fallen over.