I dont know if its common in the anywhere else but in my town here in germany the stealing of bike-PARTS has become very popular. I guess the owners of high-value bikes use better locks, that are actually hard to break ( like those: http://ebay.muskelkater-sport.de/fahrrad/schloesser/bordo-gr... ). But for Parts the risk is even lower and a good break or light system can yield a few bucks.
I personally use a cheap ( 50€ ) used bike as a daily driver, in combination with a 30€ lock, there will mostly be an easier/better target for the thief and if it ever gets stolen, its just 50 (80) bucks and not 1000€.
Yup, very popular here in SF. I recently just got my wheels stolen. Also had a few seats stolen as well. Stealing parts is probably more common than stealing entire bikes. And if you look at the pictures of the stolen bikes linked in the article, most of them are missing a front wheel, which to me, implies that the thieves were targeting bikes that were only locked by their front wheel (or they were selling the front wheels of the bikes, as those are pretty common theft targets as well).
I personally use a cheap ( 50€ ) used bike as a daily driver, in combination with a 30€ lock, there will mostly be an easier/better target for the thief and if it ever gets stolen, its just 50 (80) bucks and not 1000€.