Once-obscure patent filings are giving companies PR headaches. Walmart promised once again not to engage in dynamic pricing. CEO John Furner wrote Friday in an online "Letter From Our CEO" that the retailer "doesn't set different prices based on who you are or the time of day." The question has percolated for Walmart all year, fueled by its new digital shelf labels and a pair of patents—one to dynamically update prices online and another to recommend prices based on anticipated demand.

Walmart told the Financial Times in March that neither patent was about dynamic pricing. The retailer said the first focuses on markdowns and the second is a tool to inform staff decision-making. But that didn't convince everyone.

Meanwhile, Prada pursues a lavish strategy to turn very important clients into even bigger spenders.