After being 'randomly selected' again, whilst in uniform, I asked the security person "why do you pick out the crew members all the time". His reply was, "because we have to do a certain number of searches per hour and you guys aren't allowed to complain. It's just easier this way".
Given that this indicates that the selection of people to screen is not random then a letter of complaint should be written.
I haven't asked them recently but I will next time I'm 'got' and if that is the response then I'll send some paperwork in.
Of course, eventually the word will filter down to the screeners and instead of giving us the honest answer they'll come back with the 'random' response.