This is great for them by encouraging people to put the most ridiculous and outlandish one star reviews possible on Yelp, in hopes that their review will be turned into a T-Shirt. They'll be left with positive reviews and off-the-wall negative reviews that no one will take seriously anymore.
I'm definitely eating lunch there today, even though it isn't hacker news.
I went there and no one was wearing these shirts. Delicious food, and still not Hacker News.