diberry - 2:45 pm on May 7, 2013 (gmt 0)
So informational sites bounced up on 4/15 while stores saw a decrease.
Again, NONE of my info sites saw any change in Google on or since April 15, except my Penguinized one (which may also be slightly Pandalyzed). So whatever this is, it's not affecting all sites equally. I think it's Penguin.
1. Could it be that some external event, such as the Boston marathon on 04-15 made people change their internet behavior for ONLY a few days, which then sent (temporarily wrong) signals to Google (i.e. "time on site"), which then updated the SERP based on these updated (and temporarily wrong) signals? That would mean that it would fall back at some stage.
This is really, really important to remember. I'm not sure it applies in this case, but I think we're all underestimating how major events impact the SERPs. It used to be they simply pulled people offline and onto watching TV, so nothing changed online - there was just less traffic. But now suddenly people who would normally spend all day on Facebook are glued to CNN instead, and people are searching for stuff they normally wouldn't, and NOT searching for stuff they normally would. It HAS to send some funky signals to Google which eventually get cleared up.