A few years ago, I suspected that there might be a counterfeit version of my Saving the Planet ebook circulating. Additionally, we have a textbook author in my husband's family tree, and textbooks are supposed to be particular targets for counterfeiters. So I can imagine these victims' pain.
But as an Amazon customer, I also have concerns about making sure I'm not buying fakes and thus undermining other authors. I'm not sure how to do that, unless I make a point of avoiding all third-party sellers, the honest as well as the dishonest ones. Which I certainly can do.
UPDATE: I just stumbled upon Summer Reading Prime: How to Avoid Buying Counterfeit Books on Amazon from Nancy Mertzel, an attorney specializing in copyright and trademark litigation.