Bruce Schneier picks up a story about the police putting warning stickers on vehicles with tempting parcels for the casual thief. [Conyers Police Department warns shoppers to protect valuables in cars, Rockdale Citizen, Friday, December 07, 2007] Bruce thinks the police are just helping the thieves.
In London, the Metropolitan Police put up notices, apparently addressing car thieves, advertising "Free Satnav in this area". Presumably the intended effect is to remind car owners not to leave their satnav in the car.
In contrast, in the city of Leicester, the police have resorted to handing out free cloths, to wipe the satnav marks from the windscreen. [Source: Leicester Police website] This appears to have exactly the same intended effect - to remind car owners about the vulnerability.
Obviously there is a risk that these warnings may sometimes trigger crime rather than help prevent it. But the principle of publishing vulnerabilities is based on the assumption that this information helps law-abiding people to defend themselves from attack more than it helps the attackers. (There are lots of comments in Bruce's blog discussing whether the same principles apply here as to software vulnerabilities.)
Even if these measures resulted in a short-term increase in the levels of crime, they might seem justified if the longer-term effect was to teach car-owners better security habits.