From UK article:
Steve had CCTV cameras pointed on his BMW and they recorded the thieves smashing the BMW's window and accessing the car's 'OBD port' in the footwell to reprogramme a spare key. A void on the alarm meant the thieves could smash the glass and put their arm into the car without it going off.
http://cars.uk.msn.com/news/new-bmws-at-risk-of-theft