Spammers can and do forge approvals. Servers which do not accept the moderation will continue to propagate spam. Propagation of messages outward tied to site where moderation is done. Would prefer creation of new group to moderation of existing one, but will probably grudgingly concede. Business as usual.
Group remains unmoderated, spam continues to pour in unabated.
Requires no effort whatsoever. After untold millenia, the stars align and the denizens of alt.sex.cthulhu perform terrible rituals under the baleful light of alien suns which summon the Great Old Ones back to Earth. Spammers get eaten by a shoggoth. Billions of unopened Twinkies, preserved eternally by the foul magics used in their creation, become mankind's sole legacy to the Universe. If I've missed any options, please let me know so I can update this list.