they were just trying to improve user experience it looks like, as detailed in this post, "Sniff browser history for improved user experience."
http://www.niallkennedy.com/blog/200...ory-sniff.html
"The social web has filled our websites with too much third-party clutter as we figure out the best way to integrate content with the favorite sites and preferences of our visitors. Intelligent websites should tune-in to the content preferences of their visitors, tailoring a specific experience based on each visitor's favorite sites and services across the social web."