James Shore has an excellent article on how you will fail with Scrum and other agile methodologies if you don't to realize the importance of engineering practices such as XP, TDD, Automated Acceptance tests etc. If you don't you'll probably end up with an ever increasing amount of technical debt that is going to fail your project. (hmm, increasing debt seems to be the theme this year:) )
One part that got me laughing was Ken Schwabers analogy about Scrum and your mother-in-law
"Scrum is like your mother-in-law," Ken Schwaber said at the recent Agile Vancouver conference. "It's constantly pointing out your shortcomings."
Having practiced Scrum for a while I must agree that this statement is spot on!
Just for the record: This is of course not true for my mother-in-law :) *** Gun against my head ***