I think searchers on average are getting smarter about searching. They may still run really generic searches using 1-2 words, but they now understand that they will improve upon those results by refining them with an additional word or two.

For optimization purposes, a site is clearly best off if it can rank high for the least number of words possible in the search phrase, then also rank competitively for the phrases containing additional terms. This should generate the largest percentage of targeted traffic.

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- Ed Kohler
Web Marketing by Haystack In A Needle