According to a recent New York Times health article on push-ups, a 40 year old woman should be able to do 16 Full push-ups in a row without rest, and a man of the same age should be able to knock out 27 push-ups.
The article states that push-ups are an excellent measure of fitness because they work so many parts of the body at once, not just the back, chest, arms, and shoulders as some people think. Your core, glutes, and leg muscles must also be held rigid while you perform the exercise with only your hands and toes on the floor. The ability to perform multiple push-ups is an indicator of an individual's strength and endurance, measurable factors which may help them as they age since up to 30% of a person's muscular strength can be lost between the ages of 20 and 70.
Now if that isn't enough to get you people on the push-up band wagon, I don't know what else will. I am going to continue doing them and I am confident that I will be happy with the results. I'm sorry to leave you, but I have push-ups to do!