I usually remove any materials where mold has set up house. Bleach has to directly come in contact with the mold before it can be effective.
I think with pourous materials bleach just doesn't have that ability.

JR ... check some of the links Randall and Bob have posted and you'll get some good info.

How's it going Jaz?

Ok, I'm out numbered.

I'll bite the bullet and review what I currently believe is correct about mold and bleach.