Just read this on their blog, it has been in place for a few weeks now. Great news, I have a develop account so plan on using this new feature in the Linking Open Data kind of way.
Here is a quote from the blog:
I’m absolutely positive we’re barely scratching the surface, and people like David will set me straight, but at least we’re making forward progress - 150K SmugMug accounts now have auto-discoverable FOAF, embedded XFN, and are OpenID endpoints.
What does this mean for you? It means, hopefully, that SmugMug can play nicely with other social applications on the web. Your network of friends & family is now published in machine-readable formats so that other networks can do intelligent things with that data. How exactly this will happen remains to be seen, but there are lots of bright people thinking about it, so hopefully it’ll happen.
At the very least, when the Semantic Web actually works in the year 2022, SmugMug will be ready. 
It is good to see that such a great photo sharing site (SmugMug) has such forward looking developers.