http://www.guardian.co.uk/worldlatest/story/0,1280,-5226907,00.html
WASHINGTON (AP) - Asking for increased vigilance in the wake of the London bombings, the government is warning that terrorists may pose as vagrants to conduct surveillance of buildings and mass transit stations to plot future attacks.
Singling out as a threat those who are the least able to defend themselves sounds pretty chilling. What could be easier than rounding up homeless people? Just declare them to be terrorist suspects, and a significant percentage of the country will believe it just because the government says so. And another significant percentage just won't care.
It's too much of a foot in the door. Once you get used to mass roundups of the "usual suspects", it gets that much easier to expand who is a usual suspect.
And does the idea make much sense in the first place? People actively ignore vagrants - that is not the same as not noticing. The question of who goes without notice is a tricky one - you really have to think about who you don't notice, because they have escaped your notice.
The people you don't notice are the people who look just like everyone else - neither especially attractive nor especially unattractive; dressed like everyone else, neither overly well-dressed or overly shabbily dressed; ordinary hair, etc. People may actively look away from a vagrant, but a perfectly ordinary person barely registers on people's minds.