Not sure if the OP saw it here, but this was in an article titled Foam Factors: Advanced Brewing in the Jan/Feb 2010 issue of Brew Your Own magazine.
I'm at work now, so I don't have the article handy, but I recall them citing alpha acids aiding in head retention as well.
"We brewers dont make beer, we just get all the ingredients together and the beer makes itself."
~ Fritz Maytag, President Anchor Brewing
Bottled: AHS Red Stripe Lager clone; AHS American Amber Ale; Apfelwein/Cyser, Coffee Stout
In Primary: Nut Brown Ale, Apfelwein
On Deck: Anchor Steam clone