agent_x - 4:44 pm on Mar 27, 2012 (gmt 0)
I wonder if this has something to do with their "natural language search" efforts. Perhaps Googlebot wants to view the page as a human does in order to learn more about how humans interact with the pages? That would make sense to me.
I've thought this for a while. Google doesn't just need to render your page to provide the preview image in the search results, it needs to know what your page looks like to know where the content is, how many ads you have above the fold, etc - surely?