Each time you sign up for a new site you create a profile which is unique to that site. You’ve got to upload a picture and fill everything out. It’s a pain to keep up with it all, which is why I haven’t yet added my picture to my Digg or LinkedIn profile.
MySpace has launched the Data Availability initiative which can make MySpace your home base for profiles. With this new initiative you’ll be able to integrate elements of your MySpace profile on partner sites that so far include Twitter, eBay, Yahoo! Instant Messenger, and Photobucket.