1. A method comprising: in response to a user visiting a site at which the user may engage in any of a plurality of behavior patterns, performing the steps of: determining a source domain from which the user is visiting the site; based, at least in part, on the source domain, selecting a behavior pattern, of the plurality of behavior patterns, in which the user is likely to engage; and customizing the user's experience at the site based, at least in part, on the selected behavior pattern; wherein the method is performed by one or more special-purpose computing devices.