When you deactivate a Facebook account, it asks you to choose a reason from a number of radio button options, or provide your own. The following is the text I cobbled together on my iPad to inform Facebook why I was leaving:
I'm uninterested in where facebook is going. I recognize that I am the product and not the customer on facebook. This is a compromise I've been willing to accept because of the number of friends, family, and colleagues I have who use it. However, as of the recent ui change and #f8 announcements, I'm done. Not only is the interface worse than ever, but I have no interest in my information being moderated through your algorithm, and I don't want to contribute any more of my information to your database. I'm willing to forgo large swaths of content my friends would like to share with me at this point because as far as I'm concerned it's not worth being your product in exchange for that service (and the ui sucks).