Fact: Ruth Bennett's percentage was 477 times the margin in the original gubernatorial vote count in Washington's 2004 election.
Observation: Those who voted for Ruth Bennett, in effect, cast their votes away, having no real say in the outcome.
Fact: Were the 2004 election run again according to present rules, Ruth Bennett would have already been eliminated.
Observation: Many of those voters might have considered Gregoire or Rossi, were they forced into the choice.
Observation: A margin-sized bloc of voters, thus cast about in an open sea, might have made the major candidates work harder to secure their votes in the general by bringing their issues to light.
Conclusion: Thus, it's possible that the top-two primary, by eliminating a weak third party from the running, could make those party's voters more sought-after, and hence more powerful, in any year with a predicted narrow margin.
Addendum: But probably not.
Update: David Goldstein has the same brainwave, except funnier.