Greetings Iancumihai:

A YouTube application would be awesome.

The one feature that is really needed is the ability to record a video off the N800 and be able to post it right away on YouTube.

Actually, a better site that has more potential would be Daily Motion.
They are beginning to accept HD Video.

If you can intergrate this feature into your apps, then many users will be able to VideoBlog instantly.
This is a great feature for businesspeople, students, journalists, bloggers, etc.

Iancumihai if you need beta tester I can help.

Regards Robert