God I wish this wasn't something that I had to worry about. I hate having to go to such precautions to keep some jerk from stealing something that belongs to me. Oh well...
My guess is that given enough effort, any of these could be defeated - but you hope that it's enough to deter a thief from trying. I don't leave my bike locked in particularly bad areas, and I don't tend to leave it for more than an hour or two, so I guess I don't need to worry so much. But still....