Joe Talmadge said:
Because by two weeks they're already filled with germs.
Agreed!
What exactly is the issue with just throwing it in the dishwasher with your dishes every couple of days?
You ever notice if you try to clean a very dirty sponge that you can keep squeezing it and squeezing it and dirty water still comes out?
I suspect squeezing is more effective at cleaning the interior of the sponge than the spray action of the dishwasher.
While the dishwasher will sanitize the sponge, and clean the exterior, I suspect it will leak grunge onto your dishes throughout the whole cycle. Yuck.
Everyone, certainly the microwave or the dishwasher trick is better than nothing, but seriously: Go buy yourself a small pile of
dishcloths ($4 for a set of six!, although you can get fancier ones) maybe a few extra kitchen towels. Twice a week throw them in the laundry and put out a new set. If you can't handle twice a week, do it once a week.
Something too big a job for the dishcloth? Just use one of the kitchen towels and then throw it in the laundry.
-john