Rimshot - I believe you are correct the shield does protect the other players from flying sticks, drool and other questionable things which spew forth from the drum riser (the work really well with projectile vomit, etc) naturally this requires cleaning of the shield every few months (in particular if left in the band truck on hot summer days).
gitrokr - the drum shield's primary purpose is to limit bleed from the drums into other stage mics. The shield does little to limit the sound - in fact from a drummers perspective it actually makes the drums sound louder, since the sound reflects off the shield right back at the drummer (it makes the cymbals almost unbearable).
Drum shields deflect sound but do not absorb sound. Now you could build some panels with sound absorbtion which could ut down some sound - but to really eliminate the sound it would have to enclose the drummer (which may not be to a drummers liking).