well one main cause of that rust forming at the rear wheel wells for older hondas is because of a rubber piece covering the rear wheel fender (i think thats what its called). All the salt and stuff get stuck there and that causes the rust. You just peel the rubber off from the rear wheel fenders. Doesn't seem to hurt anything to remove it.
Did this for my 96 accord, and I hear 98 accords and up no longer have it.