Canon has issued a product advisory for the Canon 6D relating to the inability for movies shot on the 6D to playback on YouTube. This appears to be aimed at users who pull a card out of their camera and upload directly to YouTube.
The fix (for now) is to save the file via ImageBrowser EX and then upload to YouTube. If you already go through an editing and exporting process for your HDSLR videos, then you don’t need to worry about this problem.
Tamron recently started a new video learning series on YouTube. The series will be comprised of 1-minute videos geared toward new DSLR owners (like the above intro video) and will be added on a weekly basis to Tamron’s YouTube channel.