I have had the same on one of my betting sites this weekend. Scary indeed, went from positions 1-3 for a set of juicy keywords (variations around a keyword that I've held for around 6 months), down to number 19-21 on Sunday morning, then looks like they're coming back to their normal places this evening. Who knows what the future holds for these rankings!?
The change to remove ads from the right hand side has just washed through, I wonder if there was some testing associated with that update that's caused a bit of fluctuation recently.
Up to 4 ads now at the top apparently for 'highly commerical' search terms. Plus 3 at the bottom. Organic space becoming more and more lower down the page.
Google will make changes in the next two months as they already announced.
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