22. The system according to claim 16 , wherein the threshold is tuned for an application.
16. A system that ranks search results, comprising the following means stored in a computer memory: means for determining relevance of respective search results selected from one or more of a Usenet, a discussion thread, a blog, an archived community discussion, or a chat room via one or more feature-based relevance functions, wherein the features are based at least on one or more of global thread properties comprising at least a thread depth, one or more posting-specific thread properties and attributes of a person generating the postings, and wherein the attributes comprise at least a number of posting per time duration, a number of newsgroups posted to and a number of postings that have no responses; means for generating the one or more relevance functions that facilitate ordering the search results based on their respective relevancies, wherein the search has variable scope based at least on a structure of a thread comprising one or more messages comprising at least a message core with text of a single message within the thread and a message body including text of a plurality of messages structurally related to the single message within the thread, at least one of the features is based on labels on edges between a message in the thread and one or more of a parent or child of the message, wherein the labels are automatically inferred from content of the one or more messages within the thread; means for defining a threshold for an acceptable relevance for at least one of the one or more relevance functions to mitigate providing non-relevant search results to a user, wherein the threshold is dynamically adjustable to adapt to the user's response to returned results by raising the threshold when the user rejects a portion of the returned results wit ha relevance above the threshold; and wherein the threshold limits the returned results based on system level constraints.