IMHO threads like stupid question and answer help to reduce spam in other threads. I see it so: There is(was?) average, 4-5 stupid answer-questions there every day, Without that thread, they would probably appear sooner or later somewhere as spam. So yes it helps to fight the spam(well, to be more precise: to acumulate it in one meaningless thread, where it dont bother anyone)
And yes, it is good thing to have when you want to write something like:OMG YOU RETARDED STUPID NOOB!!!!IT WAS ASK 123456789 TIMES IN THE QUESTION AND ANSWER THREAD BEFORE!!!!!!!!