Some nice new Web 2.0 action going on over at Threadless, which has overhauled it's profile pages to incorporate feeds from Flickr, Last.fm, del.icio.us and MySpace, plus a generic RSS option.
The net result is far richer profiles with minimal additional effort from the user. It's a neat illustration of the power of syndication feeds in aggregating personal data and it's just the tip of the iceberg. A profitable next step could be the development of an XML-based standard for tagging individual elements of a user's profile (e.g. their favourite books) to facilitate the easy sharing of this data and save them from having to enter it countless times on different sites.
There may even be call for a service with the sole purpose of aggregating users' feeds and providing them to other sites via a single login. Imagine if, rather than having to build a fresh user profile every time you start using a new site, you could just type in a single username and password which would automatically retrieve all relevant profile fields.
Aggregating user profile data inevitably raises some interesting privacy questions. Maybe you don't mind someone accessing your Flickr photo stream in isolation, but when it's coupled with your Last.fm history, your del.icio.us links, your MySpace page and your blog posts, someone has a whole lot of insight into your life: the photos you've taken, the music you've listened to, the friends you've added, the sites you've bookmarked and the thoughts you've blogged, which, when you put it like that, is kinda scary...