I've noticed various molds growing on the bedding of my worm bin since I started it. I've never been too worried about them as I figured they were part of the decomposition process. I have found some interesting (to say the least) mold formations growing out of the ventilation holes in the side of my bin since it's come indoors for the winter. After reading this article I found out that it might be from feeding my bin too much. I was worried my worms were not getting enough to eat so I was a little overzealous the last time I fed. I'm going to stick to the 1 to every 2 weeks I've been feeding them, since that seems to work best for my bin. When I feed it's what I feel is a good sized bowl full of scraps. I keep the scraps in a container in my fridge so they can break down a little prior to being added to my bin (the worms will eat them faster this way). I've been wiping down my bin frequently to prevent the mold from reoccuring, and added more fresh moist newspaper bedding on top. If the mold comes again I will take a picture of it.
http://www.allthingsorganic.com/How_To/12.asp - Read this article for great information on all of the other wonderful creatures living in your bin, how to cope, deal, and just realize that they're your friends too.