Flew BWI-LAX-FAT last night.
BWI-LAX they grabbed the first two for screening, and then each time a screener finished with someone, they grabbed the next person to pass through the line.
I was darn tired by the time I caught the 10:16pm RJ up to FAT. I meandered over to the line and wound up first. They tagged me over for special screening. I said, "ah, the curse of being first in line, right?" and the screener said "yep."
I replied, "then it isn't very random, is it?" She shrugged and said, "we just have to keep busy screening someone."