The growing popularity of online dating sites is altering one of the most fundamental human activities of finding a date or a marriage partner. Online dating platforms offer new capabilities, such as intensive search, big-data based mate recommendations and varying levels of anonymity, whose parallels do not exist in the physical world. In this study we examine the impact of anonymity feature on matching outcomes. Based on a large scale randomized experiment in partnership with one of the largest online dating companies, we demonstrate causally that anonymity indeed lets users browse more freely, but at the same time impacts the existing social dating norms (what we call a weak signaling mechanism) and thus produces negative impact on matches. Our results show that this weak signaling is especially helpful for women, helping them overcome social frictions coming from established social norms that discourage them from making the first move in dating.