Came to this via ThomasK's recent post.
'Losing' valuable knowledge inside forum postings is something that has exercised me in the past - so often after a longish period, the same subjects and questions recur, as the previous answers and threads vanish from visibility inside the forum.
Another thing is unanswered questions - you wonder if the questioner ever found out a solution, and if so, why couldn't he have let us all know !!
Keyword searching of old posts can help, but what is missing is semantic filtering - the person making the post is in a good position to categorise the information in the post, but doing this every time might become tedious.
Perhaps the "subject areas" is a good idea, but rather than forcing a post to go into one particular 'box', hereby presupposing the post is only applicable to one area, if the posting form had all the possible subjects as checkboxes at the bottom, the poster could tick all the categories felt to be appropriate.
Therefore if a post showed how to use EA to link requirements to a use case, the ticks might go into 'EA HowTo', 'Requirements', 'Use Case' ...
Then you could search / read by selecting one or more of these categories, in one browsing mode.
This might be adequate to improve things sufficiently, while not requiring undue effort from the poster. Of course, posters could just ignore it, but then they would be denying us the fruits of their labours !!
I suppose in a true collaborative spirit, we would be able to vote posts into additional categories ...