Today I was trying to register with youtube but without success. I was only getting this message: "Sorry. Based on the information you have submitted to us, you are ineligible to register for YouTube.com". So I Googled a little and found this information on Yahoo Answers posted by Sappho:
I just read through the Terms of Service, and as long as you are over 18 years of age you should have no trouble signing up. Double-check to make sure you put in your age right, and that you have not signed up with this e-mail address before. If it still gives you trouble, try a different username. Usually if a username is taken, the site will tell you so, but perhaps YouTube hasn't programmed their site to do so. There is nothing in their TOS that indicates that anyone from a particular region is ineligible to register, so your location shouldn't be a factor.
If you try all of this again and are still having problems, I would contact YouTube customer service. There may be a problem with the system.

My problem was that the username I was trying to register with is taken by someone, but instead that YouTube gave me the reason of the error, I was redirected to this page http://www.youtube.com/signup_copa ;)
I simply changed the username and I registered without problems :D