I notice that foam on beer seems to disappear quicker for some people more than others (and not just because they drink faster!). Does this have to do with breath, stomach acidity?
Indeed it does do that – but my guess is that the answer lies more in the glass (or your lip gloss) than in the drinker's gastrointestinal system. The foamy head on many styles of beer is prized by the cognoscenti. The science is worthy of (and probably has been responsible for) a few PhD theses. It has much to do with the chemical structure of proteins and hops, but the difference from one glass to another, when we're talking about the same beer poured from the same keg or bottle, mostly concerns factors external to the brew.
Those glorious suds can be slayed by a variety of factors. As a sworn enemy of dirty or poorly rinsed glassware, I would speculate that the main culprits are dirt and soap. Foreign residue in a less-than-pristine glass can interfere with foam's chemical structure, leaving you with a headless brew.
But, as you hypothesize, the drinker may play a role, too. Waxy, oily components in, say, lipstick can do the same. I'm not discounting the possibility of saliva "backwash," either, as unsavoury as that is to consider.
But if you sniff your (foamless) brew and it smells like soap, don't hesitate to politely let your server know. You might just score yourself a free pour in a cleaner glass.
The Flavour Principle by Lucy Waverman and Beppi Crosariol (HarperCollins) won top prize for best general English cookbook at the 2014 Taste Canada Food Writing Awards.