Besides leaves and dirt getting clogged in your fan?
Just look at all the dirt and crap it blocks.

I agree, it blocks a lot of crap, however most of that crap is just dust particle size. The largest things I had in there were tree seeds that were the size of peas. All that stuff should easily make it through the vents without clogging anything. My question is if anyone knows for a fact if there will be a problem by leaving the filters out?

The microfilters were originally intended for people with allergies that need to reduce pollen, and also to help remove dust from the air. I could care less how much dust and pollen I inhale, or how often I need to dust my dash board.

I am sure the quantities are too small to be of any concern. Almost anything can be considered toxic in the right quantitites. You will die if you drink too much water. The real concern with the filters is for allergies or people with asthma that might be more sensitive to particulates.

I don't follow this statement, do you mean them catching fire because the filter is clogged, or because the filter is removed? A dryer is very hot and is a different circumstance. Can't really compare.

When those filters clog up, it will greatly reduce the ACs efficiency, which will in turn increase the load on the blower fan and likely cause reduced life. To fix the problem I have to change my filters more often (or simply remove them). I don't want to replace $40 filters every couple years that don't really serve any purpose other than to reduce allergies or make people feel like they are breathing cleaner air. I don't live in a dusty environment and I don't have allergies.