"Yes" button Claims

A "yes" button

allows the user to verify a significant action
is commonly used in modern software and should be understood by most computer users
but having to move the mouse and click the button causes extra actions to be required to implement an activity the user has already initiated [GOMS]
but "Yes" may be misleading, perhaps the button should just read "Logout"
but "Yes" is not consistent with the use of the "Go!" button used to login