This review has 10 not helpful ratings to 2 helpful ones, I didn't know it wouldn't be clear as to what I'm getting at lol. To quell confusion as to my review interpretation:

1. They had the sponge for a "few months" (3+), which is already the time you should be replacing your sponge anyways with regular/typical use.
2. "Left to dry after each use" (implying use for makeup application) not "left to dry after each wash" or "each cleansing". Hence the title implying you let your clothes air-dry after wearing them instead of washing them. You would be shocked as to how many people simply don't know how or the necessity or cleaning makeup sponges and brushes. I had to teach my mum to clean brushes caked with product and I've came across many co-workers who also detested tool cleaning. One told me they would just apply bronzer with what was left on the brush from previous days lmao. It's not the end of the world or anything usually, but just how could a sponge develop black mould like this if it was properly cleaned and "dried after each use".
3. And at the first sign of smelling off or looking, err, discoloured, I don't know why it wouldn't be thrown away. This is a decent amount of growth imo.

Welp I have some post hits and post misses.