From Cameraphone Prohibition (on Mobitopia):

It's the same story as with DRM for audio. If I can use my senses to experience (see, hear) something, then I can use recording equipment to capture that experience.

A collusion between vested interests (who desperately wish there was a technical solution for restricting the spread of content) and organisation keen to sell snake oil (ever seen a DRM solution that worked and provided a pleasant customer experience?) is to blame IMHO.

If camera-phones are enough of a threat to your organisation that you're attempting to "jam" them, physical security (i.e. searches and confiscation of any devices etc.) sounds more appropriate.

On a slight tangent, some camera-phones are polite enough to make a noise (often a sample of a traditional camera click) when taking a photo. Perhaps aural cues like this - to alert people in the immediate vicinity that they're being photographed - are more of a long-term bet, but a future where you are alerted when a picture is taken seems more realistic than one based on technical or legislative restrictions.