diberry - 5:33 am on May 25, 2012 (gmt 0)
I'm seeing shifts several times a day, for me and for my competitors. Can't tell if it's different datacenters serving up different SERPs or what. I go up on one term, down on another, and then a few hours later it all switches up again. But the oddest part is that suddenly the amount of traffic I get from Google.com (not counting other Googles) is almost identical three days running. So the volume of search isn't shifting at all, but the terms bringing visitors to me are shifting all the time.