In response to Eric Posner's observation that "security theater" has some beneficial effects: Yeah, sure, so stipulated, but that's not the point. Rather, we should ask ourselves whether the benefits of theater outweigh the costs?
With regard to 5a it may very well be the case that some terrorists will be deterred, but the false sense of confidence engendered by ineffective security measures may decrease overall vigilance on the part of travelers and airport staff, thus allowing security breaches which might not otherwise have occurred. Similarly, with respect to 5b, the increased sense of security may cause some people to travel who might have otherwise done so. At the same time, however, some people may choose not to travel by air due to the additional hassle that arises from such theater as forcing people to take off their shoes. There's a balance between costs and benefits in both cases and it is far from self-evident that the balance favors the appearance of security over actual security.
Absent evidence to the contrary the above suggests that the appropriate approach to take is to favor truly effective security measures over those which are highly visible but do little to improve actual security.