I always prefer a 1:1 relationship with providers: that is, an account that's tied directly to me rather than through a third-party provider like Twitter, Facebook, or OpenID. (Aside: why is social media managing my passwords? On the third option, it's great in theory and terrible in execution.)

My biggest issue with Flickr is that they tie it to a @yahoo.com email address. I know it's part of the "ecosystem", but c'mon—who uses one of those?