Wikia has a demo of Kaltura's collaborative video editing tool here. Kaltura's MediaWiki extension allows you to collaboratively create and edit videos, music, images, and animations directly on the wiki.
Please try it out and let us know what you think of it. We are very open to bug reports and suggested improvements and I will make sure any comments get passed on to Kaltura. See the help page for more details on how to use this.
If you can think of some cool uses for this tool on your wiki, please let us know. This will also help in the development since we need to know how people are most likely to use collaborative video.
I feel this has a lot of potential to enrich the content of many different wikis, so please give it some time and see how you could use it.