Now this is a interesting thought, photographer Stephen Gill says he wear a DayGlo west when photographing in public to be left alone. We all know public workers wearing DayGlo, they are everywhere and nobody stop for a moment to think about what they are doing, after all, they are wearing DayGlo. I have a DayGlo west which I have used on commercial shoots now and then.. but the idea is that maybe I can work invisibly wearing it for street photography... this must be tested.
Bill also mentions this on his blog about shooting in the street. click to read "the Invisible man".
This is part of the SEP "Somebody Elses Problem" effect - Read the Wikipedia entry.