Bruce Schneier doesn't mince words about the stupidy of (a) using biometric IDs to create two classes of travelers (low risk, higher risk) and (b) privatizing the system that does it:
What the Trusted Traveler program does is create two different access paths into the airport: high security and low security. The intent is that only good guys will take the low-security path, and the bad guys will be forced to take the high-security path....The Trusted Traveler program is based on the dangerous myth that terrorists match a particular profile and that we can somehow pick terrorists out of a crowd if we only can identify everyone. That's simply not true. Most of the 9/11 terrorists were unknown and not on any watch list. Timothy McVeigh was an upstanding US citizen before he blew up the Oklahoma City Federal Building....What incentive do these [for profit] companies have to not sell someone a pass? Who is liable for mistakes?
Need more reasons this is could be a bad idea? What Bruce doesn't link to is a blog he wrote the other day about how Holland's biometric passports have been cracked. On the other hand, it's not like the credentials accepted by airports today can't be easily forged. So, maybe anything that raises the barrier to forgery is better as long as it applies to everyone and it doesn't give anyone (the TSA in particular) a false sense of security. One other point: soft targets in combination with the potential for a lot of casualties seems to me to be the biggest area of vulnerability. In the bigger scheme of things, between the security in the airports, the security on the planes, and highly sensitized passengers (who, historically, since 9/11 have acted pretty quickly at the first sign of a threat), airliners are not exactly easy prey. I'm not saying that we should have the best security possible in airports. It's just that I can think of some much softer and very populous targets that could use equal if not more attention.