Inspired once again by Mr.Incredible aka "The Commentator", I have a question for you. If someone has a filthy, dirty, disgusting microwave oven, is that fact alone a good indication of their general cleanliness? I don't know what it is about microwaves, but the food splatter they create when you're too lazy to properly cover your food as it waves, or clean up your ugly mess after the dish stops rotating, is a major yuck factor for most otherwise sane people (and I say "yuck factor" because, hey, the microwave is a technology to cook food that is of fairly recent origin, though it is not something people are adverse to using, except when the inside of a particular oven is covered with the remains of old food).
I once had a friend with a disgusting pig of a daughter, and because I would sometimes spend extended evenings there at her home, and often get the urge to heat a snack in the microwave, I was actually forced, under the ruse of a Christmas gift, to buy her a new microwave, because the one she had was so covered on the inside with crusted food particles that it was literally black. I advised both her and her offspring to take good care of it and clean up after microwaving, but not 2 months later, the new microwave was in the same condition as the previous one. I should add that her daughter also had a cat whose litter box she never cleaned (poor cat) and a room that was so unkempt it even made me (I'm notorious for Oscar Madison syndrome) nauseous.