[JohnWoo]

Still want to say few words for left joins
Lets say that you have large board with many forums, usergroups and complex access level. After it lets suppose that somebody with common access level (just registered) will search for some common phrase (for example "+javascript +flash").
On one board, where i tested it, such search with no left joins return nothing because fulltext query find first 200 matches in forums invisible to beginner members and stop on it. Showresult page (looking on current member access level) hide all that 200 matches from search result and with great enthusiasm say that nothing found On same forum search with left joins return complete set of 200 matches (from other forums visible to beginner members) for same search phrase and may return more if "maxresult" will be set to larger number.
But if your forum access level structure is not too complex, you may remove left join part without visible consequence