Given that Lagunitas' trademark is of the logo, and not the letters "IPA", their claim (as @pagriley points out) is about the context of Sierra Nevada's use of the letters--font, placement, style.But given that, I think this is a pretty big overreach here. They are essentially claiming that they own the trademark on any use of "IPA" when those letters are 1) large and capitalized, 2) in the center of the packaging, and 3) darker than the surrounding background.I honestly want to see this one go to court to see how a trademark judge would rule regarding whether or not the Sierra Nevada version is unique enough to avoid infringing on Lagunitas' trademark. Aside from the incredibly generic standard that Lagunitas is asking to be upheld, they are ignoring the fact that the likelihood of confusion between these two packages is extremely low, given the prominent placement of the Sierra Nevada logo as well as the distinct branding look/feel of the Sierra Nevada brand vs. the Lagunitas brand.A question for anyone who knows more about trademark law than me--is there a possibility of Lagunitas losing their trademark on the IPA logo by taking this to court if the judge decides that their trademark is too generic?It's really a bit sad that a company that has done a pretty amazing job of cultivating a recognizable brand through the use of pretty generic branding would feel the need to sue to protect it's brand in this way.