Just as a quick aside, I'm at an IT security conference. As a fun semi related activity, they taught us how to make a lock pick, and how to pick locks.
They then gave us some locks which had been modified so we could see what was happening inside, and some pad locks ranging in price from $2 to $80. The big difference was the number of pins and the tolerance of the pin inside its shaft. The less play in the pin, the harder it was to pick.
I'm not going to describe the process here to give anyone ideas, but to give an indication of how easy most locks were to break, a 2 pin lock was broken in 10 seconds. A 3 pin lock took about 30 seconds, and a 4 pin lock took about 5 minutes. I couldn't break 5 or 6 pin locks that hadn't been modified. Remember that I have no experience picking locks whatsoever.
Moral of the story is, make sure you get a good pad lock with a lot of bumps on its key (indicating a lot of pins in the lock)