Well, I am for an open web, especially in the linked data/semantic web sense. That said, Facebook, Google, and Twitter make it really easy to export your data. Just to be sure about Facebook, I just went to my account settings and requested a data dump, which is happening right now. Similarly, I like to periodically dump my GMail, Google documents, and Blogger blog posts. It seems stupid not backing up your own data. I don't back up G+ data but I use G+ mostly just to link to my long Blogger blog posts. For a public presence, people should really own their own domains. Blogger makes it really easy to assign your blog to a subdomain that you own.
I take a few steps to maintain a modicum of privacy: I log off Facebook after looking at family and friend's posts, and I often run Chrome in Incognito mode because I think that it makes general web browsing a little safer.
Whatever this data dump from FB consists of, is it in some usable form? My understanding is that it's a pdf without any ability to import it into any other software. For example, can you import birthdays directly into iCal (or w/e) or import email/ phone #s into your desktop or mobile addressbook?
I take a few steps to maintain a modicum of privacy: I log off Facebook after looking at family and friend's posts, and I often run Chrome in Incognito mode because I think that it makes general web browsing a little safer.