First off, thank you for your interest. I'm humbled that so many people have found this work interesting and discussion-worthy, and I welcome the feedback generated by additional readers.
When I first posted the visualization to my website, I did so with the best data that I had available, and explained its origins and caveats as clearly as I could. I also released the original chart under a Creative Commons Attribution/Share-Alike license, since I wished to invite my potential critics to make "better" versions of the chart themselves, thereby benefiting the broader discussion of privacy and Facebook.
Since then, I've made several corrections and categorical revisions to the chart based on input from my readers, and I believe this process is still ongoing. I hadn't anticipated the scale of the response to this graphic, nor that the corrections might alter its details to an appreciable extent.
The result has been that many bloggers and news organizations have appropriated older and less-accurate versions of the graphic for themselves, making it less likely that readers would click through to find the most up-to-date version. Some even copied and pasted the entire contents of the site (minus the corrections) into their own template, making it appear as though I had written a feature for their publication and harvesting the resulting ad revenue.
As a researcher, I am committed to accuracy, openness, and accountability in my work. I feel a personal obligation to ensure that things published in my name are as complete as possible, and that my readers are easily able to see corrections and revisions.
Therefore, with regret, I withdrew the Creative Commons license from the current version of this website beginning on May 15th, 2010, and retain full rights to its content.
From this date forward, you may not create derivative works from this content, except as follows:
You may NOT use this visualization or site contents in print, without contacting me first and receiving my permission to do so.
I'm a strong believer in free culture; once I am satisfied that this work has been finalized, my intent is to once more release it under a CC license.