I just saw this the other day for the first time when i went on SS on work. i thought it was really annoying. i usually stay logged into SS on home computer and couldn't remember my password.
although, it is a much better implementation than some sites use, limiting you to a certain number of page views then requiring you to register. that's so annoying that i don't even bother requesting my lost password from years ago on mind & muscle when i go over the view limit