Cc-by-sa plus main page attention is a very good reward for professional photographers, particularly if they get dual FP status on Commons and en:Wikipedia. I wrote an article about this for a business publication a few months ago where I crunched the Alexa numbers and concluded that a day on that main page is considerably more valuable than below the fold placement on the front page of The New York Times.
For the most part, the people we're trying to reach:
A. Don't realize this is an opportunity.
B. Are in the habit of retaining full copyright.
My argument was that judicious relicensing can be a very smart move for portfolio material that no longer generates revenue streams, particularly in terms of generating viral links and incoming traffic to the photographer's website.
I wouldn't mind writing up a photographer-specific variation on that article for a photography magazine. My e-mail is enabled; mail me an editor's name if you know one.
-Durova