In a lot of fantasy set in generic medieval Europe equivalent, one of the stock characters is the plucky street thief. (Steampunk, as well, and any story involving a bazaar.)
But where does your plucky street thief come from? Who is he going to sell your stolen invention to? What is the black market in stolen goods?
..Did you know most stolen items are sold within an hour of their theft, and often within 5 minutes? Or that low-level thieves in present-day Manchester target soap and Mach III razors - precisely because they are hard to prove stolen, and easily disposed of (everybody uses soap)?
Or that there's a highly enterprising con that involves buying cheap gold-looking jewelery / knock-off copies of luxury goods and reselling them at a higher price on the black market, all the while acting like they're the stolen real deal?
Go, read. http://www.academia.edu/465485/How_Prolific_Thieves_Sell_Stolen_Goods_Describing_Understanding_and_Tackling_the
One last note: while people are people, and the entire report is a very interesting and illuminating window on the world of thieves, it is also Extremely English. This means they're blinded by their own worldview. Very sharp people put a lot of thought and effort into trying to figure out how to disrupt the economics between thieves, fences, and the not-so-innocent buyers... and completely ignored any risk involved from anyone other than the police. I assure you, thieves in Texas and Tennessee put a lot more effort into figuring out if they're going to get shot by the homeowner than thieves in Nottingham and Manchester, and that appears to be a far greater deterrent to crime right there, than anything this paper proposes as a solution.