1. A computer-implemented method, comprising: using a first computer-implemented system to receive an activity stream, wherein the activity stream comprises a first plurality of computer-implemented objects, wherein the objects are temporally sequenced; selecting an object of the first plurality of objects as a context for a recommendation; and receiving a recommendation of a computer-implemented object, wherein the recommendation is generated by a recommender function executed on a processor-based computing device, wherein the recommender function generates the recommendation based, at least in part, on an inference of the recommendation recipient's interests from a plurality of usage behaviors and a contextualization, wherein the contextualization comprises affinities between the selected object and a second plurality of objects.