1. A method for identifying obsolete discussion threads in a forum, comprising: extracting a plurality of keywords from a discussion thread, wherein the discussion thread comprises a plurality of postings posted by a plurality of users; assigning an initial keyword score to each of the plurality of keywords; identifying a change event, wherein the change event is a change affecting a topic of the forum; extracting a keyword from a recorded medium recording the change event, wherein the recorded medium is separate from the forum; comparing the keyword from the recorded medium with the plurality of keywords from the discussion thread to identify a matching keyword in the plurality of keywords; decreasing the initial keyword score of the matching keyword to a decreased score for the matching keyword based on the matching keyword matching the keyword from the recorded medium; aggregating the keyword score assigned to each of the plurality of keywords to obtain a total score for the discussion thread, wherein aggregating comprises using the reduced score for the matching keyword; and displaying a warning on a user interface comprising the discussion thread when the total score is below a first pre-specified threshold.