How can I tell if my MacBook's iSight has a hardware problem?
If System Profilier isn't showing it up under USB then the iSight has been physically damaged beyond repair (not accepting power) or has been somehow disconnected from the Bus. System Profiler always displays connected devices, even if they're corrupted or non-functioning.

Take your Mac to the Apple Store and they will tell you what it will take to fix it. The most likely scenario is that it will be a free repair, and they'll clean up your computer while they're at it :)

If you can't get to an Apple Store call 1-800-MY-APPLE and ask them about your options.