A system, apparatus, and method are directed towards enabling information filtering using measures of an affinity of a relationship between subscribers of an online portal system. The affinity of a relationship may be determined based, in part, on the tracking of various online behaviors of and between subscribers of the portal system. Any of a variety of behaviors may be tracked, including message communications between subscribers, participation in instant messaging groups, purchases, activities, categories, and so forth. Such behaviors may be employed to determine a level of trust (or affinity) between subscribers of the portal system. This affinity measurement may be used to filter various information, including, but not limited to, product recommendations, ratings, polling queries, advertising, social network communications, personal ads, search results, and the like. Moreover, this affinity measurement may also be employed to perform message spam detection.