I was under the impression the G1 only played properly encoded .mp4s, but today I received a forwarded email via my gmail account that contained a .wmv attachment.
The G1 game me the opportunity to 'preview' the .wmv, and of course I tried it, fully expecting it not
After a medium length pause, the video did indeed play back using the built in 'youtube' player on the G1.
If anyone would like to download the file and email it to their gmail accounts to test, I have uploaded it here:
Apologies if this was already known, I did a forum search before posting and did not find anything.