YouTube of gaming?
Are you serious?
People don't PAY for YouTube.
People SHARE content, tools, ideas, concepts.. they can help each other.
XNA will never take off outside of the indie developer niche. The public will never buy into XNA. There will never be enough people involved in XNA for it to reach that same kind of mass as YouTube.
Give them free tools, Give them a free platform, Give them free content to work with. Sell the best content back to the community and make money, I think Jaffe might be on to that kind of idea, and by extension Sony.