I have taught the multifactor test for trademark infringement four times now (using the 9th Cir. Sleekcraft test), and each time, some student has questioned which way the "strength of the mark" factor should cut. As a matter of current doctrine, stronger marks receive a broader scope of protection. But smart Stanford Law students who are not yet indoctrinated with longstanding trademark practices ask: in practice, isn't there less likely to be confusion with a strong mark?
In their new article, The Scope of Strong Marks: Should Trademark Law Protect the Strong More than the Weak?, Barton Beebe and Scott Hemphill expand on this intuition: "We argue that as a mark achieves very high levels of strength, the relation between strength and confusion turns negative. The very strength of such a superstrong mark operates to ensure that consumers will not mistake other marks for it. Thus, the scope of protection for such marks ought to be narrower compared to merely strong marks."
The doctrinal relationship between trademark strength and protection was not always as clear as it is today. For example, Beebe and Hemphill point to a 1988 decision by Judge Rich of the Federal Circuit: "The fame of a mark cuts both ways with respect to likelihood of confusion. The better known it is, the more readily the public becomes aware of even a small difference." This more nuanced approach to consumer confusion also finds support in many foreign trademark cases.
To be sure, Beebe and Hemphill are really making an empirical claim about consumer perceptions, and the evidence base is quite limited (though they cite some related studies at notes 102-03). But as they note, the current doctrine relies "on a jumble of untested empirical assertions," and their argument makes a good deal of intuitive sense. At the very least, this article should spur trademark scholars, practitioners, and judges to reexamine their understanding of the relationship between strength and protection. And the next time one of my students asks about this, I'm glad I'll be able to send Beebe and Hemphill's work their way.