In the present chapter, we seek to understand the actual social use bilinguals make of a minority language. To this end, we isolate some of the factors that in‡u- ence their language strategic behaviour. We argue that bilinguals have linguistic preferences and face both linguistic coordination and communication optimiza- tion tasks. Further, we take into account that anonymous interactions are fairly frequent in present modern multilingual societies, making the linguistic type (bilin- gual or monolingual) of interactive partners private knowledge. Thus, bilinguals’ language choices are often made under uncertainty. To reach fast language co- ordination smoothness and communication e¤ectiveness, bilinguals tend to build linguistic rules or conventions. The emergence of those conventions are shaped by the economizing laws and principles of least e¤ort in human communication, politeness strategies, and other elements, all combined in a context in which the minority languages are competing with the communication capacitiy and power of the majority languages they are in contact with. We show how the strategy use the same language as your interlocuctor may become popular among the bilinguals, and how this strategy is the source of their failure to coordinate in the minority language.