(UPDATE: The source photographer is MANNIE GARCIA, a Washington D.C. based freelancer on assignment for the Associated Press in 2006. Click here for more.)

Ironically, just hours before President Obama was sworn in, there was a flurry of activity on the Obama-poster-photo-source front. I received a number of emails and comments on my MYSTERY SOLVED! post.
There is a brand NEW photo a couple of photo detectives found that looks better than the Reuters photo. It has the entire necktie and shoulders, it's facing the same way, and has all the same highlights and shadows - even on Obama's collar - as the iconic Fairey poster.
Steve Simula created the evidence above for his Flickr page using the Obama headshot he and a few others out there found (just as Fairey did originally) by doing their own Google image-searching. It looks to be an Associated Press photo made sometime in 2006 or even earlier.

I am at a rest stop on I-95 driving home from covering the Obama inauguration, so I can't look into it now, but I have every confidence someone out there will find a version of the photo that still has all of its metadata and caption info intact. Let us know!