Been frustrated with with BlackBerry and Youtube player to watch videos on your Blackberry. Yes, absolutely you can watch on your Blackberry Phone. After trying hard to view Youtube on their website you will be ending with error message..
The only way I found to play YouTube Videos Directly, by installing BlackBerry: http://boltbrowser.com/boltbb.jad This browser will allow you to play directly without any issue.
The second method to play videos by installing http://www.vuclip.com/Launchers_Apps.html
By installing these two Applications, you will be able to play YouTube Vidoes and VuClip Videos.
Congratulations and Enjoy Watching..