Cable locks are next to worthless. ALL of them. Okay for securing an inexpensive front wheel only.
If you want your bike to not be stolen, you need a top quality u-lock from Kryptonite or OnGuard (not the $20 models...the good ones start at around $35 or $45 and go up, up, up). That u-lock needs to go around your rear wheel just behind the seat tube and be attached to a beefy steel pole that is set in concrete. Use the cable lock to secure your front wheel.
From time to time, I'll see a $2,000 bike parked outside Krogers. There is no lock made that will guarantee total protection. I'm comfortable locking a $400 bike on the street. No thief is going to spend ten minutes with power tools fighting to get his hands on a $400 bike. However, folks with a $2,000 bike need to buy a "beater" bike for trips to the store...no lock is totally theft-proof.