Those who cannot watch youtube videos directly on mobile can follow this procedure to view them:
1. Go to http://vuclip.com
2. Click on "I am on mobile"
3. Then search for videos like you do on youtube
4. Results will be displayed.
5. Click on any video. It will convert that video into mobile format at runtime.
6. Once converted click on low-res or hi-res format to view or download.
I tested it on my blackberry and it worked like a charm.