I've always thought of it (palm facing outward) as a dual purpose sign. I have always been told that the backhanded "peace sign" was "the bird" in England, so I never used to use it that way. Nowadays, in the Hip-Hop era, the backhanded "peace sign" means exactly that "peeeeeace".

Taken from ooze.com...

PALM-BACK V SIGN
Gesture: The peace sign, but reversed so the palm faces the recipient
Location: Jolly 'Ole England

If an American was visiting England and saw someone give them the palm-back V sign, they'd probably mutter, "Damn hippies". Yet the Englishman wasn't offering a symbol of peace, but instead telling you, "up your bum!".

In the British Isles, the palm-back V sign has the same meaning as the finger, but with a cockney accent. It's use can be traced back to the 16th century, but it's hard to pin down. Whether it was first used as a variant of the cuckold's devil's horns, or as a variant of the more ancient middle finger, but with some extra fingers thrown in to make it that much more painful is unknown.

In 1941 Winston Churchill made what we now know as the 'V-for-Victory sign' famous. He made no distinction between the forward and palm-back V sign until the latter part of the war when someone probably pointed out he was telling the masses to, "piss off". As always, those wacky elites really had no idea what the peasants were cooking up. This general confusion was exploited by American antiwar protesters in the 60's who used the palm-back sign to secretly tell the police to off without getting themselves a one-way ticket on the Kent State Express.

 

I rev, and flash the lights. I throw up the peace sign if they wave or somethin.

 

Me too, but I give them our Tampa S2000 card. I had an S2K follow me down the highway when I was in my Kia Rio (don't make fun ). We got to a toll plaza with 10 booths. I made sure he pulled in behind me at the same booth. I give the lady working the toll booth my toll, gave her extra money to pay the guy's toll in the S, and have her hand him my card. The guy in the S was appreciative and caught up to us in traffic to wave, but that was over a week ago and I never heard from him.