hard to believe (well actually not considering some of my coworkers) that many CRRs couldn't figure out what the STA identifiers were..
As for having them on the vehicles.. most of ours don't have anything, and we have a few other STA identifiers on others..
As for challenging strangers, you don't have to get in their face, just yell "HEY WHO ARE YOU" then you won't get blown up.