SEONoob - 5:14 pm on Mar 13, 2013 (gmt 0)
I'm sorry but I don't serve personalized results for googlebot. The only thing I do is to base on the visitor country to show content specific to country, and on the device used to show content adapted to mobile (the HTML don't change much, but sometimes I hide a not-so-useful div in order to gain space).
My only sin is to do only half a dozen of banner exchange on my homepage. All my competitors do the same, far worse even, and they are still first page. I honestly/humbly don't think this is related to the 90% search engine drop I was inflicted on March 6th.