I always use a lock at the resort, but I also always keep my board in sight. You have to realize that all you're doing with a lock is hopefully making a thief look for an easier target. The reason I use a lock is so someone can't just grab my board and go. Since I have my board in sight, I'm hopefully going to see them trying to cut the lock or remove the binding and hopefully that'll give me time to get out there and knock his ass out. Again, the key word here is "hopefully". In my mind, a lock is cheap and worth the insurance it provides.
locks, especially thin cable snowboard locks are a deterrent, not a guarantee. a would be thief is going to scope out an unlocked board before a locked one. my local resorts have a free snowboard check, i always use that.
I used to have one of the basic Burton locks with the three digit wheels. I locked my friend's board along with mine while we grabbed lunch and the combination wouldn't work when we got back. I noticed the plastic casing was a little bent so I pulled it apart a little further and saw that one of the wheels wasn't sitting correctly. Long story short I just bend the thing off and solved the riddle by moving one of the wheels one digit form where it was supposed to be.
Gave me a scare so I stopped using locks (my board was also old), but now that I have new gear I'll invest in something better.