ohno - 10:27 am on Mar 28, 2012 (gmt 0)
Looks to me they are split testing,no way the SERP's can change this quickly. Two data sets, one with Product Search results at the top & no images, the other with organic results at the top with image results below the fold. No Product Search one box on the second set. No doubt this will show them how much the Product Search box is worth (at the cost of Adwords!). Wait & see.