Okay, how come the link comes up as "not found" for me? Did we drive tpoo much traffic to it?
Yup, hte left arm up is a vestige of pre-turn-signal days for cars. I think maybe we remember it at all 'cause it's weird :-) I find I'm so right handed that it's easier to make a right turn with that right hand on the handlebars, but as often I'll point with my right hand anyway. I have a blinkie for a left signal but I can't always get the switch to work... I'm thinking of getting some bar end lights (I have flat bars) like http://www.knogusa.com/en-us/dept_6.html
I also use the dork factor. I got a Hi-Viz Camelbak and put a blinkie on it. I've got a little blinkie 'way down low on the back, and a ***big*** (reellight or realite, I forget) 8 x 5 blinkie in the left bag and a WTF "wonder wand" that blinks through five colors on a little plastic moon (it's a kid's toy that my friend got me 'cause she figures the more lights I have, the better). That and the HOkey Spokes ... I didn't even have 'em all going but a kid says "ain't nobody gonna hitchu!" as I ride by...
Cars really do seem to have a more automatic "treat you like a slow car" response when you are *in* the road acting like a car than when you are trying to stay totally and completely out of their way. And I do try to be overtly nice & friendly... and they tend to be, too.