Considering that the Coursera certificates require you to take a class (usually taught by experts in the respective field) as opposed to cramming for a certification exam, I'd say it's a good bit more valuable.
I took the first AI class last Fall, and if you've never been exposed to the material, it was a very good survey of Artificial Intelligence.
I agree, just as long as the certificate actually means you've taken the course and done the work. If one can cheat one's way through the homework and then just cram for the final, the Coursera certs would end up being of low value. I hope not, though. I'd love to have a good way to tell the continuous learners from the people who get stuck.