You really should click through to io9 to see this amazing infographic detailing just how many sharks are being slaughtered every day for their fins. The number is 11,417 per hour, but the graphic is really what puts this practice into perspective.
On a slightly related note, I had shark filets for dinner a year and a half ago and they were absolutely fantastic - tasting like white steak. I always feel slightly guilty for eating fish, given all that i hear about the incredible damage we're doing to our oceans by overfishing them, but a friend of mine caught the shark in a fishing competition, not as part of an industrial operation, so I figured it was okay. Damn was it good - it's an experience that will stick with me for a long time.