I have just canceled my Pro subscription. It was scheduled to renew in two days from now. I also deleted almost all of my thousands of photos from the service, most of which were set to friends and/or family.
With increasing frequency I am added as someone's contact on Flickr. Upon closer inspection it often is someone who has very little to show for in the photo stream, but has tons of pictures of toddlers and babies favored, and has an extensive contact list of the owners of those photos. I can only imagine what nefarious purpose that may serve.
Of course, I block these individuals, but it made me rethink my privacy strategy.