Good questions @jeff3. Don't know the real answers, but I'll share my opinion. I think duplicate content is the main issue at hand. Secondly (especially for the bigger Youtubers), duplicate earnings as well, which feels a bit like trying to have it both ways.
Time of the day really depends. There have been some articles about posting between certain times on certain days, but hey, if everybody posts then, it would clog up the news feed. For me the problem is that by the time I'm done editing and uploading for the day, its past midnight on US east coast/South America and still early morning in Europe/Africa. For the Asian timezone it would maybe work, but for me it really feels I'm posting at the middle of the night.