This is page 4 and NO ONE has mentioned the fact that at the LQS you can get a protecter to prevent the blade from reaching your fingers.
It has a small plastic curved "wave" that sticks up over an inch and deflecks a blade up into the air rather than across a finger. To put them on a ruler just peel off the shipping tape and CAREFULLY place it on your ruler where you want it. Once down, it doesn't come off.
My DH saw it and bought 2, one for each of my 24" rulers (my favorite cracked and I still use it when I'm doing a cut over 24" and can't fold the fabric). Sometimes I grab the ruler and use the wrong side.... the other day he caught me at it and growled so I'm trying my darnest to use the ruler the "right" way.