Regarding similar programs in the Bay Area: "none of the five agencies analyzed for this study measures the effectiveness of their campaigns. Whereas they all have a similar goal—to increase passenger awareness about security issues—little evidence therefore exists confirming whether they are achieving this goal." [http://incaseofemergencyblog.com/2010/09/17/new-study-indica...]

Shneier doubts it's effective either [http://www.schneier.com/blog/archives/2010/05/if_you_see_som...]