Delete, deactivate or Close YouTube Account: Simple Steps

Follow the steps below:

1. Sign in with your username and password. 

(https://accounts.google.com/ServiceLogin?continue=http%3A%2F%2Fwww.youtube.com%2Fsignin%3Faction_handle_signin%3Dtrue%26feature%3Dsign_in_button%26hl%3Den_US%26next%3D%252Fchannel%252FHC0KTfvckXa4E%26nomobiletemp%3D1&passive=true&service=youtube&hl=en_US&uilel=3)

2. Click the "My Account" link in the upper right corner.

3. Under Account Settings, click the "Delete Account" link.

4. Enter the reason you're closing the account, and your password, then click the "Delete My Account" button.

5. Click the "Log Out" link in the upper right corner. 

Note: 

You may still see thumbnails of your deleted videos on the site as the site takes a while to update and synchronize. Please be assured that your videos have been removed from the site and the thumbnails will be removed from the site soon.

Read More:

http://support.google.com/youtube/bin/answer.py?hl=en&answer=55759

http://howto.cnet.com/8301-11310_39-20080196-285/how-to-delete-your-youtube-account/

http://www.youtube.com/watch?v=3iSGlCYnLq0

http://answers.yahoo.com/question/index?qid=20090506141700AAPfcUl