I've heard some stories recently from companies who have "tried Scrum", etc and have given up on it or believe there is minimal value from it. When I discuss the results with individuals from those companies there is a common set of reasons:
1. Scrum was used as a micro-management tool. A command-and-control manager was looking for a way to get more work out of the teams and told them to "use Scrum". The team attempted to implelement it but there was no "Agile champion" or coach around to coach the team and the manager on ownership. Self-organization didn't emerge and it Scrum died on the vine. I refer to this as the "Cargo Cult" approach to adopting Agile :).
2. Too much team ownership emerged. There were no effective customers or product owner and the teams ended up owning their own product. Real product value growth was no where near what was anticipated.
3. The team/company/publisher could not get a handle on planning beyond the iteration. Planning was still done in large documents, long term milestones were still in use, etc.
I hope that we can share some "failure stories" on the mailing list. Not only would the stories help those trying to adopt Agile, but many people have expressed that they'd like to try Agile again in a different environment and don't want to drop thinking about Agile completely.