Have you tried mixing two Media-RSS feeds using Yahoo! Pipes? If not, check the following Yahoo! Pipe, it’s mash up of YouTube and Flickr Media RSS feeds.
If you look at the output xml, you would notice there is no media-rss (module) elements(media:content, media:player etc). Yahoo! Pipes removes all media module specific elements which were present in original feeds (in this case: Flickr and YouTube).
This is not usable because I am loosing my data and I couldn’t even figure out a way to add namespace declaration, if you know a way please let me know.
I am tired, going to sleep
Update (14/08/07): Yahoo! Pipes team has fixed this issue. Yahoo! Pipes now emits media-rss tags. Check out this thread.