A couple of weeks ago, one of Debian's most active developer Matthew Garrett threw down the towel and called it quits protesting against the Debian's rather strong democratic culture of having a free for all discussion about any decision making pertaining to Debian making him intensely irritable and unhappy. He went on to compare Debian's lack of civility and slowness in decision-making with the more structured way in which decisions are taken at Ubuntu.
On the backdrop of Matthew's exit from Debian, Mark Shuttleworth himself has chosen to respond to and clarify Ubuntu's position in relation with Debian on his blog.
And his opinion is that Ubuntu (and many other Linux distributions based on Debian) can never survive without Debian.
He goes on to state that Debian's chief strengths is its uncompromising emphasis on free software. He dwells on some of the short comings of the way Debian is managed and believes that at the end of the day, some introspection is healthy and that Debian will benefit from the discussion.