Errr... so the trust model of the PSTN is fine as long as everyone who participates is trustworthy.

Whereas a "stupid network" requires the sender to assert something about who they are and then the recipient has to ascertain the truth of that with reference to a third party of choice (and that choice is allowed to not be the ITU). [Whether Verisign is less evil than the ITU is left as an exercise to the reader.]

Trust isn't transitive; only by being closed and static can the PSTN survive. The Internet is Darwinian-style evolving organisms highly resistant to attack. The PSTN is not, and has no resistance to Packetian Flu. The only possible outcome? See http://www.telepocalypse.net/archives/000453.html.

Martin, Your point is well taken. But the point here is not PSTN vs. Internet; I am of the opinion that that point has been established. Given PSTN's weakened state of immunity, I am asking whether we should ban infection (as being pursued by FCC) or should it avoid contact so as to protect itself.

SIP has RFC3323 and 3325 which implement some privacy extentions, most important the P-Preferred-Identity and P-Asserted-Identity. We yet have to push our first product using these into full service. I expect it to do the job but it also introducted a non-neglectable risk of other ISPs (your airports) to not verify these headers and somehow an asserted number is fake.