If you have a very controlled cave, where you've got the mould spores you want in there, then the high humidity will help them grow. However, in most home caves, you've got what's in the air, so all sorts of wild moulds will call your cheese home. These can still produce some great results despite looking a bit awful. I find regular brushing helps to develop a nice rustic wild rind, and I'm generally pleased with the results. However, if I don't clean the ripening boxes and the cave every so often, the wild blue moulds will take over. And they are not the good tasty blues of Stilton etc.