The thing that is irritating to HM Customs here in the UK is the camera phone! The use of cameras in the customs hall has always been expressly forbidden.
As most phones nowadays have cameras, I would think this prohibition of mobile phones is going to become standard policy in Customs Halls worldwide.
Mobile Phones could also be used to alert smugglers that customs officers are watching them or a whole raft of other sinister purposes (indeed, the LHR baggage handlers found the texting system very useful in assisting with pilferage a few years ago!)