Glass bead blasting is fine for any material you don't want damaged by more abrasive mediums like garnet or worst still, sand. These include aluminium and magnesium housings and to some extent the ground finish on lightly scored/scuffed crank shafts before re-polishing of bearing and seal areas.
Internal parts as Suzuki27 suggested I feel are fine to blast with glass as long as you make sure parts are FULLY dismantled before being blasted so glass beads don't get lodged in hard to get places and can't get cleaned out. When blasting is complete, all part should be throughly washed in a suitable solvent to remove any residual glass dust and blown dry, then all threaded holes should be re-taped to clean out threads and machined mating surfaces should be rubbed or lapped on a surface plate of 600 grit + wet and dry to ensure full sealing of gasket faces is achieved on reassembly. These proceedures should be normal practice during all engine rebuilding to ensure an accurate and efficient assembly.
Remember, if you can't fully dismantle an item and remove every nut, bolt, bearing, seal, shaft, circlip (everything) then don't blast it, those beads get in everywhere.
It all comes down to how particular you are with your cleaning and pre-assembly stages that determines the success of the final result of the piece of equipment you are rebuilding.
