Originally Posted by justageek
My guess is that missydarlin has it exactly right. Human Factors 101 says that if you build a technology with a non-zero false error rate, the human operators will soon learn to ignore the error messages. This is true with all the warnings you get when you use your web browser, and it has also been cited as the cause of some airplane accidents (pilots assume the warning is erroneous--"that warning light comes on all the time"--and just ignore it).
I don't see a way to fix it in this situation. As missydarlin pointed out, passengers do lots of things to their BPs that render them unreadable, thus a "false error." GAs are already under pressure to board the flight quickly, so the chance that they will invoke the manual override is extremely high.
You are absolutely correct about the pressure on the gate agents. They are just trying to get the people on the plane. Also, in SEA last night, we used a common use gate on the N concourse that apparently doesn't have an AS scanner. The agent entered the seat number manually (the old fashioned way). You could see how that might lead to all sorts of problems.
Overall, I am less concerned about bar code scanners than I am about the abysmal on-time performance (two flights this weekend with 90-120 minute delays).