I have no idea why I think this or how this came about but...I think real flowers on something you're supposed to eat is dirty and weird and insects may have laid eggs on them.
I got goosebumps looking at this particular example from Buzzfeed:
Also, can we stop trying to make "naked cakes" happen? They aren't going to happen. They are fugly. Just cover it with buttercream if you don't want to peel off fondant.
Anyway, whenever I see real flowers on a cake, I just think, "Those flowers were outside. There were probably insects on those flowers. They might have laid eggs. Oh god, they're on the FOOD. Those are NOT food-grade flowers. You wouldn't put your bouquet in your mouth, would you? Why would you eat cake impregnated with insect eggs???"
So...yea. There's my weirdest irrational fear. Besides zombies. I think, for some reason, that zombie apocalypses are absolutely possible and that I will wake up one day to a zombie mom and a wasted Earth.
*Edited to indicate pet peeve is a tad bit irrational due to indoor flower growing and the fact that lavender is edible but apparently gross
UPDATE: The truly wonderful Pastry Chef In Residence, There-Was-A-Corpse-Danced, has (somewhat) assuaged my irrational fears of flower-borne insect eggs and other nasties by commenting that there are, in fact, food grade flowers.