Well, it depends on the type of forum and the type of results you want to present to your members. My forums are content oriented and finding heaps of irrelevant search results only confuse the person and make it rather hard to trace the most relevant thread.
eg. if in my forums i search for a word :
Banda Singh Bahadur (dialect)
Now, this search under natural search option returns full 11 pages of search as it provides information about any thread that contains either of the three words present in that thead like Banda,Singh,Bahadur. And the most relevant result for the search was figuring in around 7-8 page of results... useless to members in my case as nobody ever bothers to go through 7-8 pages to find the most relevant result.
Now, if we make the same search under Boolean search option, it returns only 2 pages of search results for those threads which contain the complete phrase "Banda Singh Bahadur". And the most relevant result was the 5-6 topic in the first search results page itself!! How happy my members would be to find that topic, i can well understand.
You can test this example right on my forums -->
http://www.sikhphilosophy.net
I have already suggested this to vb.com to make this option to be in the hands of the admin to allow boolean or natural search option. --> here :nervous:
Till then enjoy this mod !! :devious:
Regards