alarm system can be defeated. definately. but remember the TIME factor. the more TIME it is needed to defeat the system, the less a target you will be.
it is stupid to say just because your car CAN be stolen you decide not to install an alarm system. then, you might as well not lock your doors on your house, cause the padlock can be broken.
an alarm system is NOT a prevention system. it is a deterrent system. and you should do more reading, for example, the Clifford Avantgard G5, paired with the wireless immobilizer, whats there to cut? i always say that an alarm system is only as good as the installation, you can have 3k worth of alarm equipment but if its installed by a joker, the wires expoded, brain not hidden well, then it defeats the purpose. but if its done by a real professional, the thief would probably have issues even if the alarm brain was exposed.