Marshall - 2:35 pm on Apr 28, 2012 (gmt 0)
Based on some tests I have been running, I believe Google might be taking two more factors into consideration: Rich Snippets and Open Graph Protocol tags.
I have noticed is past SERPS that many snippets seemed misleading which leads me to believe people were spamming/gaming results with them. Lately I have noticed fewer snippets being displayed in SERPS.
I also put some erroneous information in a OGP tag referencing another site and WMT now shows a link to that site where none exists within the page. This makes me believe they are reading the OGP tags and are treating them as sources of spam/gaming results if the information is not an exact match to the page content.