Here is my horror story about letting a cake sit out: I was making a very large temple cake for my daughter's wedding. The cake board it was on wasn't going to fit in my freezer so, before I put it on that board, I called my daughter across town and asked her to measure her freezer. She said it would fit. I expected it to take a week for me to make this cake but it only took a couple of days. I hauled it across town to her house, only to find out it didn't fit in her freezer. So I took it home and set it on top of my pellet stove (not lit) for several days, figuring it would be fine. This was in May in Mt and it snowed on her wedding day, so it was fairly cool.
At the wedding reception, a friend of mine was serving the cake. She and I stopped to take a break and have a piece of cake. She cut us each a piece of cake and she scraped the moist bottom of the cake that stuck to the bottom off and put it on her plate, saying that was her favorite part. The reception was a dance so it was rather dark in the room and we took our cake into the darker kitchen and started to eat it. She took one bite and said, "Something is wrong with this cake." We turned the light on and found moldy cake on her plate. Mine was fine and everyone else's was too because the cake had broken off at the moist point as she was serving it. I was horrified and just prayed that we didn't make anyone sick and was thankful that it was my own daughter's cake and not one I sold to someone.