Great article, Daniel. My debit card was definitely skimmed last season. I'm pretty sure it was probably at an ATM in a tienda in Sayulita, because the only other place I used it was at the bank in Melaque (though I guess it's possible that it was there - I'm sure not a pleasant thought for many of you reading this).
Anyways what happened was that for some reason my debit card wasn't working suddenly a few months ago when I went to an ATM and then at a grocery store. So, I dropped into my credit union to let them know. Well, turned out it was them that cancelled my card. They asked if I'd been in Mexico lately. Well, yes... Then they explained that the crooks often wait until several months later and then do a whole run of cards and that this was happening a lot in Mexico lately. I guess they had tried to use my card but the credit union/bank system fraud protection caught on immediately and nada was gone from my account.
Be careful out there amigos...