Shared preferences are a critical component of social attraction. Knowing that someone likes the same things as you do is indicative of broader underlying similarities that support successful social partnerships. However, not all overlaps in preferences are equally informative. Here we propose that the rarity of overlaps in preferences may be a particularly salient cue for social affiliation. We find evidence that people are sensitive to the rarity of overlaps in preferences and affiliate themselves (Experiment 1) or predict others' affiliations (Experiment 2) with potential social partners who share a relatively rare preference. Because preferences provide information about both what people know and what they like, we also tested the effect of overlaps in knowledge (without taste) and overlaps in taste (without knowledge) to understand why we are drawn to people who share our preferences.