This action really bugs me and it is an example of the me generation run amuck.
By flushing with your foot, you are actually picking up germs from the floor (the actual dirtiest part of the bathroom) and depositing them on the handle so the next innocent person who is not germ phobic to pick up on their hands.
Please stop flushing with your foot and if you must take a few sheets of toilet paper and use your limb with the opposable thumb to flush the toilet.
And stop papering the seat and also just plain flush the damn toilet.
An article on germs in the bathroom: http://abcnews.go.com/2020/Health/story?id=1213831&page=1