I've witnessed this first hand - we recently started rolling out measured goals in our warehouses. This involved staff getting set daily goal counts for certain tasks (products shipped, products put on shelves etc.). As soon as we rolled out metrics everything that wasn't measured became a low priority. For example, we were not measuring cycle counts (stock take) so immediately the number of cycle counts plummeted, which increased our out-of-stock errors. We had instances of staff hoarding incoming shipments from suppliers at their workstations in order to get higher rankings.

Overall the warehouses went from being generally efficient to extreme performers on measured metrics. I think metrics can be clearly powerful, but you have to be very careful about what metrics you choose to implement.