tedster - 7:01 pm on Sep 19, 2012 (gmt 0)
There was a lot of change in some SERP areas in the days preceding the Panda Update. In fact, there have been, pretty much in a row, some major changes which could be taken together and looked at a s one "big" update with several different parts. I think that's what "Bacon" is intended to refer to.
For more information on other, earlier churn the the search rankings, see Google Updates and SERP Changes - September 2012 [webmasterworld.com]