Pickpockets

Pickpockets actually like and will hang around "beware of pickpocketing" signs. The instinctual reaction of a person seeing this sign is to check their valuables, starting with their most important ones.

This makes it much easier for a pickpocket to figure out which people and pockets to target.

The easy way to avoid pickpockets is to sucker punch anyone that enters the 1 meter zone around you. In next to no time, you'll be in a cell and the police will take care of your valuables.

If you trust the police with them, is a whole different issue.