This is a good op-ed piece in The New York Times on the psychology of waiting in line (though it could have been published in the science section):
[T]he experience of waiting, whether for luggage or groceries, is defined only partly by the objective length of the wait. “Often the psychology of queuing is more important than the statistics of the wait itself,” notes the M.I.T. operations researcher Richard Larson, widely considered to be the world’s foremost expert on lines. Occupied time (walking to baggage claim) feels shorter than unoccupied time (standing at the carousel). Research on queuing has shown that, on average, people overestimate how long they’ve waited in a line by about 36 percent.
This is also why one finds mirrors next to elevators. The idea was born during the post-World War II boom, when the spread of high-rises led to complaints about elevator delays. The rationale behind the mirrors was similar to the one used at the Houston airport: give people something to occupy their time, and the wait will feel shorter. With the mirrors, people could check their hair or slyly ogle other passengers. And it worked: almost overnight, the complaints ceased.
This is also important:
When a long wait ends on a happy note — the line speeds up, say — we tend to look back on it positively, even if we were miserable much of the time. Conversely, if negative emotions dominate in the final minutes, our retrospective audit of the process will skew toward cynicism, even if the experience as a whole was relatively painless.
On that note — how can airports make the wait less painful? Maybe have some kind of reward available when you reach the scanners and/or TSA personnel.
Want to read more? The Wikipedia article on queing theory is fascinating.