On one hand there is no need to ask for password confirmation because it is annoying. If I made a mistake when confirming my password I'll need retype my very complex password again. There is also a button that can show/hide the password so I don't need retype it in order to confirm it.
However, some users don't use the password show/hide button and the 'forgotten password' option will be pain for them.
Twitter removed the password confirmation from registration but left the dual confirmation in place for changing password. Is this right approach?