1. A method for building a user language model that indicates one or more natural languages for a user associated with a user identifier, comprising: receiving an indication of a set of one or more characteristics associated with the user identifier, wherein at least some of the received characteristics correspond to a specified likelihood that the user is facile with a particular language; combining the specified likelihoods to generate a baseline language prediction; receiving indications of one or more user actions, wherein each user action corresponds to a specified expectation that the user is facile with a particular language; and updating the baseline language prediction to form a current language prediction indicating one or more languages the user is facile with, the updating based on a modification of the baseline language prediction using the specified expectations.