YouTube Video Gallery

[ZiNgA BuRgA]

It sounds like you'd have a few problems:
1. Identifying which videos no longer exist
2. Moving these videos to another forum
3. Maintaining the process (presumably you'd want to repeat this every now and then)

The last point could further add difficulties, for example, sending off 10,000 requests at a time is probably not desirable, so you'd probably need some system to stagger checks.
Either case, you'd pretty much need a custom script to do all this.