I am wondering why the link to profile looks like:
http://stackoverflow.com/users/ID/NAME
not simply:
http://stackoverflow.com/users/ID
or even better:
http://stackoverflow.com/users/NAME
Can there be couple users with the same name? Or can one user have many names?
All SO-URLs are of the form id/description where the ID is unique and the description is optional. So /users/12890/arne-burmeister
is the same as /users/12890/huhu
and /questions/420380/why-does-the-link-to-the-user-profile-have-both-id-and-name
is the same as /questions/420380/foo
. The retrieval just uses the ID, but it is much better for google ranking, when the user/question/what-ever-should-be-found occurs in the URL (also for humans this is much more descriptive ;-).
By the way, retrieval by ID is faster than by such a large text string. And of course, the URL remains valid if someone changes their user name or the question.