A slight tangent: according to Miss Manners' Guide to Excruciatingly Correct Behavior, it's a faux pas to sop up sauces with bread, except perhaps in the privacy of your own home. (Apparently, you can use bread to push something onto your fork or spoon, but you should not use the bread as though it were a utensil.) For those who are curious, the proper way to use bread to convey sauce to your mouth is to tear off a small chunk, put it on the end of your fork, and then use your fork to wipe and eat.
That said, when the sauce is just *that good*, I tend to ignore manners. While I haven't ever literally licked my plate while out and about, I have breaded with abandon and even used a finger to get the last few drops. Not particularly polite, but I was facing a wall (and I did ask my dining companions if they minded). Maybe I should invest in a little food pusher. I suspect that would get almost as many stares as licking the plate, though.