The central purpose of American trademark law (specifically, the Lanham Act) is to guard against potential consumer confusion. Of course, trademark law provides benefits to mark owners as well: it can protect famous marks against dilution, encourage investment in brand identity, and prevent competitors from unfairly trading on the brand's goodwill.

But unlike other intellectual property regimes (such as patent and copyright) the primary focus of trademark law is protecting consumers and the marketplace rather than the creators and inventors who supply it. The touchstone of a Lanham Act claim for trademark infringement is likelihood of customer confusion, and without assessing that risk a court cannot determine the viability of such claims.

In assessing the potential for customer confusion, courts in this Circuit rely on an eight-factor balancing test described more than 60 years ago in Polaroid Corp. v. Polaroid Electronics Corp., 287 F.2d 492 (2d Cir. 1961). The Polaroid factors include examination of the similarity of the products and the sophistication of the consumers in the market at issue, but otherwise do not take much account of the market context. This has sometimes created a challenge for courts faced with claims arising in non-traditional contexts such as social media tagging and keyword advertising.