Lots of info in this thread:
http://forums.ninja250.org/viewtopic...85a9e56b44f403
and here:
http://forums.ninja250.org/viewtopic...=829253#829253
Here, too:
http://forums.ninja250.org/viewtopic...ghlight=wafers
(There's some overlap in those threads!)
The keys are cut both sides, but only one side is used. It's only cut both sides so that the user doesn't have to think about which way the key needs to enter the lock. Companies that don't do this are IMHO lazy (I'm looking at you, GM!).