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Brett_Tabke - 6:10 pm on Mar 15, 2009 (gmt 0)
When I asked Matt, "why didn't they just come out and say that?", Matt said, "That's nice feedback and he would let them know".
followup: Matt Cutts stated at PubCon Austin this week that this was a test of Speed. They found that it might increase SERP speed by using ajax to fetch the results. They did not anticipate the loss of referral string information at the start of the test.