I close my browser (and all tabs, windows, and any instances of the same process) very frequently, and immediately after I'm done actively interacting with the page.

My point is, I highly doubt my browser usage pattern reflects the way the median user browses the web, and yet even my careful usage wasn't enough to keep Google from correlating enough data about my browsing's attributes (IP, sites visited, location info, logged-in geo-IP), and then expose that cross-bleed in my face.