- Why do wizards trust in appearances?
- Can we trust Professor Lupin?
- Who killed Harry Potter's parents?
- The danger of trusting your friends since they may be covertly controlled by your enemies (the Imperius curse)
- The vulnerability of certain defences against coordinated attack by several (possibly weaker) opponents. This is already indicated in Book 4, in which Mad-Eye Moody, the most security-conscious wizard in the entire series, is overpowered by Barty Crouch and Wormtail.
- Brent Dax suggests that the Fidelius Charm is a version of DRM.
The Harry Potter books can be read as a satire on technology. From this perspective, the following criticisms of J.K. Rowling are grossly unfair.
- Should Rowling be sued for teaching poor security systems to the children!?
- Logic and consistency are not Ms Rowling's strong point.
[updated to add] As Laurabelle writes in her blog, "Sometimes magic just isn’t the best tool for the job."