I guess I'm agnostic on the wisdom of federalizing airport security, but if anything I guess I favor it in that it provides a greater measure of consistency. I am certainly not blind to the inefficiencies of big government (I was a military attorney for six years and saw things in the federal civil service that blew my mind in that respect), but at least the government generally doesn't see everything in terms of costs vs. profits the way private industry does.
Most of the people here are probably too young to remember the Ford Pinto controversy of the 1970s (I was just a kid, but being raised by a judge helped me better understand the legal interplay at work). Essentially, the Pinto had a known safety problem in that the location and design of its fuel tank made the car somewhat more prone to explosion when it was rear-ended, compared to other small cars. This in and of itself might not have been a huge liability problem, but ultimately a class action suit was brought, and the plaintiffs, through the discovery process, found a memo internal to Ford, discussing the cost-effectiveness of fixing the Pinto. The memo concluded that although the existing design would predictably kill a certain percentage of people, it would be cheaper to pay off the families who sued Ford for wrongful death than to fix the car.
This is a good illustration of why privatizing airport security is, IMO, not a great idea. The airlines will do as little as they can legally get away with. The same people who decided you should have to pay for your bag of nuts (believe it or not, there was a time that a full meal was provided free on nearly every flight) are going to put as few dollars as possible into security, knowing that the actual odds of a terrorist act are relatively small, and as long as they satisfy the legal requirements, they retain plausible deniability as to their own culpability. Indeed, the 1996 Valujet crash revealed that many low-cost airlines operated under a business model of buying the cheapest used planes available and running them with as little maintenance as possible.