The magnalock rings are made out of steel, constructed with "ears" in the corners to keep them from rotating and its those ears that are held down to the rare earth magnets. Between that and the whole ring and ears setting into a machined recess, I can't conceive of them being thrown out. I really like mine and feel totally safe using them, even with 3-1/2" raised panel bits.
Then again, I *do* rotate the bit a revolution before plugging my router back in.