Nooooo! Education is something valuable for all ages. It is vital for Seniors to keep their minds sharp and acute in order to keep a healthy mind. Being a student also has its physical advantages too, with the way parking is and the way classes are spaced, you can get a ton of healthy exercise.
As far as universities taking advantage of our older citizens, this is why it is important to have advisors and staff available to all students. If an advisor is seeing that you are struggling to keep good grades and seem to be in an overall decline, they can easily recommend stopping or slowing down. So I think this is where professors, advisors, and other staff members can make our senior students more comfortable. I know as a future professor I would definitely step in if I think that a senior is being taken advantage of, and I know many professors that would do the same.
Now, it may be a waste of money as far as how expensive college is nowadays, but that is for another question! lol