Who told the security staff at Ben Gurion that CDs have been distributed as part of the welcoming pack of Wikimania? Jeromy and I were requested to show the "CD you received from Wikimania" and we haven't got any.
One of the psychological techniques used by the security agencies is to explicitly ask for something not true and wait for denial. The truth (whether there were CDs or not) is not really relevant to this question - it's how you react. Probably you are suspicious if you answer 100% questions correctly and without any hesitation. Those interviews shouldn't be treated like a school test - it's not about getting as much correct answers as possible.
For an example of a successful use of this technique, see Stanley Kubrick's movie "Eyes Wide Shut", the scene during the party at the manor (not recommended for people sensitive about explicit scenes, usual disclaimers apply).
//Marcin