"While Carnivore is potentially more intrusive than wiretaps, the FBI has proven its restraint with them, and has not abused that power. Why should IP wiretaps prove any different?"
In fact, the FBI's extreme LACK of restraint is well documented; see in particular Diffie & Landau, "Privacy on the Line: The Politics of Wiretapping and Encryption" (1999). To wit:
"Despite strictures to prevent abuses, the US government has invaded citizens' privacy many times over the last 50 years, in many different political situations, targeting individuals and political groups. Politicians have been wiretapped, and lawyers' confidential conversations with clients have been eavesdropped upon by FBI investigators.
Sometimes invasion of privacy has been government policy; sometimes a breach has occurred because an individual within the government misappropriated collected information. The history of the last five decades shows that attacks on privacy are not an anamoly. When government has the power to invade privacy, abuses occur." (p. 148)