Originally Posted by
El Cid
http://m.youtube.com/watch?v=pITRfEHKyUw
The lock in this video is a cheap crappy Master lock, and a bottle jack failed to do it. If you're buying a high-end lock (basically Abus or Kryptonite), I don't think you have to be concerned about a pry bar or a jack.
I also have the Kryptonite Fagghedaboutit Chain, which I leave at work. You wouldn't want to carry around that monstrosity, but are you locking up in the same spot every day? If so, leaving a second lock on site is a good option.
My comment on the video in question was "T
ighten up the valve!".
If you look carefully at the top of the jack it is retracting as he pumps. I (and I assume most of humanity) have dealt with hydraulic jacks and when this happens the valve is loose.