so if one of the "blades" is half open cause you incidentally bumped into an obstacle or pushed while hanging of your shoulder... you cannot notice this in your veiwfinder. right? A rhetorical question. outcomes: corner vignetting, diminished exposure. Happened to me a lot with some lenshoods not being attached properly in the past.
Thats a perfectly valid point to the robustness and reliability of this particular device. All of those little pieces, yikes. I for one just cram my 70+mm lenscaps in my back pocket or they just get pulled off in my thinktank bag when I'm getting the camera out. Lens hoods stay at home, too clunky.