I agree, but in fact Yahoo does provide the option of a me.yahoo.com/username or flickr.com/photos/username url, but by default you get some randomized URL which is impossible to remember.
I really don't like Yahoo's decision to essentially force any site which wishes to allow users to use Yahoo's login to include a stupid "Sign in through Yahoo" button. It's exactly opposite of what OpenID should be. I also don't like Plaxo's, Pibb's, etc decision to give into this and include the giant freakin' button (free advertising for Yahoo) on their sites.
Soon we're going to have 30 "login w/ x account" buttons. It reminds of the buttons for feed readers and social bookmarking sites.
Who wants to make http://addthis.com for logins?