As with all crimes, the best way to reduce occurrences is to make it not worth the criminal's while. You'll probably always have some crimes of opportunities from amateurs, but the pros would probably reconsider if they felt they could really get in trouble and that the money from the bikes isn't worth the trouble. But that's easier said than done... the police has limited resources, and they can't do everything. Maybe if one day they spend less time on the war on drugs they can spend more on property theft? If few big organized networks steal a large fraction of the bikes, dismantling them could solve a big chunk of the problem at once. Who knows...