Brian Marick recently gave a keynote at the Agile Development Practices conference; he's posted the text of the speech on his blog. It's called "Seven Years Later: What the Agile Manifesto Left Out", and is a good read about the start of Agile and where teams need to improve.
James Shore posted an entry on his blog entitled "The Decline and Fall of Agile" which gives a similar description of some of the problems many teams trying to adopt Agile have experienced. Scrum in particular gets a heavy knock, and I've seen similar results in my experience -- a team starts with Scrum and makes significant improvements in their process and planning, but the vast amount of technical debt and bad code drags the project down like a boat anchor.
Both are excellent posts and well worth reading if you're interested in Agile.