IS - since it's Amazon, you should be able to return the cable lock. Unfortunately, the promo blurbs for the item were mistaken(!), as cable locks are suitable only for low-risk areas. Besides the methods mentioned above, standard cables are easily cut with cable cutters that can be hidden inside a jacket.
If you're looking for a more-robust flexible lock, check out the armored cable locks such as this: http://www.amazon.com/OnGuard-Rottwe...ef=pd_sbs_sg_3
They're still not as good as U-locks, but at least aren't trivial to defeat.