LVMH Moët Hennessy Louis Vuitton v. eBay is a significant case that addressed the issue of trademark dilution by tarnishment, where a famous brand claims that unauthorized use of its trademarks by third parties damages its reputation. In this case, LVMH argued that eBay allowed counterfeit products to be sold on its platform, which harmed the luxury brand's image and diluted its trademarks. The ruling highlighted the responsibilities of online marketplaces in preventing the sale of counterfeit goods and protecting trademark rights.