I'm very surprised at this and I wonder if it's not a failure of the shear strength of the glue, but of the surface of the wall. I'm pretty damn sure that plaster is a crap thing to attach directly to, ditto wallpaper, and rough raw brick while strong is far too uneven to expect much contact between it and the item glued.
I think the shear strength is the weakness. I break super glued corals off their ceramic plugs for my aquarium and you can almost always get a perfect break by using flush cutters to slide the coral off the plug instead of trying to pry it off or cut it.
