I quite like this from Flickr:
We’ve launched People in Photos, a new feature that will help put a face to the Flickrverse and enable you to highlight members that you’ve photographed in a whole new way. People in Photos lets you add a member to a photo, find photos of people you know, and manage which photos you’re in.I gather from various sources that being tagged on photos without your knowledge is the thing that people moan about most on Facebook (I wouldn't know, as I flatly refuse to be on Facebook). However, it does seem like Flickr has taken heed of all that and built in a load of personal choices about who can tag you, how you are alerted and removing yourself. You can also prefer to never be tagged if you wish.
So big Twitter/Flickr hook up in 2010, anyone? That would win.
UPDATE: of course, you can tweet your pics direct from Flickr already, you just set it up like publishing to a blog.