I was opening a letter last night with my index finger as I usually do (running it along the triangle to separate it) and about 3/4 the way though I felt it grab into my skin and make a nice 1 long gash on the side of my finger.
It hurt bad. Stupid envelope. They should really make those things safer. I mean really, what do they expect a person to do, use a letter opener or a knife or a scissors or something?