With ordinary phone service, wiretapping is nearly impossible to prevent. Regardless of what equipment the phone user employs, once an agency has access to the phone line, it can tap the conversation.
With VOIP, the opposite is true. The conversation is private unless the system that does voice-to-data translation is designed and implemented to be tappable. If a terrorist wants to avoid having a VOIP conversation tapped, all he has to do is disable the tapping mechanism on his converter or use a converter that was designed without tapping capabilities. My instinct is that it will be easy to hack around any scheme for tapping VOIP calls. The only people whose VOIP calls will be tappable will be people who choose voluntarily to use tappable systems. Terrorists are unlikely to fit that profile.
...the cost of intercepting electronic communications is increasing and will continue to rise. If the FBI starts trying to dictate the design of hardware and communications systems, the social cost of wiretapping goes up exponentially. Ultimately, a costly, futile pursuit of wiretapping capability will undermine public safety, not bolster it.
For Discussion. Is there a fair analogy between the FBI trying to preserve phone-tapping capability and the music companies trying to preserve their distribution model in the context of file-swapping?