I’m asked this question nearly every week, normally in the context of a security discussion. An administrator/site creator has provisioned a site, configured security, arranged web parts and customized the quick launch to provide that oh-so-perfect set of options to the end user. But, out of the box, you can’t remove the "view all site content" link.
Mark Wagner provides the answer here (http://www.crsw.com/mark/Lists/Posts/Post.aspx?ID=36). His write-up is terrific on two levels. It provides an answer to the question, "How do I remove the View All Site Content" link? Then, it answers the immediate follow-on question: How do I easily enable the view all site content link on a site-by-site basis?
As a bonus: His approach works for WSS, not just MOSS.