Looks like the best way to collect a lot of samples is to become a developer and maintain demuxer/decoder. You may receive a lot of samples that do not decode with it 😉
I’d like to thank three major contributors (from Dania, Netherlands and Japan) of VC-1 in HD-DVD/Blu-Ray samples. It is because of them VC-1 video playback is less buggy than it was before (I know it still is but at least it’s improving).