pending hard drive failure?

Can anyone tell me if the following sound is a sign that the hard drive is failing soon? I heard a different clicking sound a few weeks ago and ran the apple hardware test on the mbp, but it came back ok. Then yesterday, it started making this noise during start up and while I was using it. I'm in the process of cloning the drive - hopefully before it dies, but I just want to see if people have had similar experiences and what it means.

http://www.youtube.com/watch?v=BF0TLyMcnis