Oh but I don't think it will be from just one picture. It'll be from a list of profile pictures you had over the years, plus your own other (non-profile) pictures, plus the pictures of you that you were tagged in by your friends, plus any other pictures that can be found through google or otherwise (flickr or picasa accounts), ...

The first versions will probably be quite crappy. Give it 5 years and it will improve leaps and bounds, plus the amount of data to work from will also increase as more photos are uploaded.

Imagine this: the software will recognize that you change haircuts every couple of months. From this it can derive that you are more fashion-conscious than others and send you targeted marketing or offers. Also it can automatically set up appointments with hairdressers, complete with 3d renders of new, proposed haircuts that you can choose from. That would be awesome, this is taking personalization to a whole new level.