What is the alternative?
I have a friend who goes to a law school where the Con law prof has a midterm and two quizzes in addition to the final. The final is worth a third, the midterm a third, and the quizzes each a sixth. This seems like a better way to gauge a students knowledge, and certainly a more fair way of grading. But the stress would kill me. Especially if all of my classes had that many examinations.
Still, it seems better than a 15 week course boiling down to a 3 hour exam.