An attempt to connect to a non-anonymous ftp server using the URL 

ftp://username@host.name.domain

fails with the message 
"Login failed" - without any detials.

Instead, Nautilus should prompt the user for the password

Of course, it is possible to enter URL in the form 
ftp://username:password@host.name.domain

(BTW: this is not documented - but this is a separate bug)
but  many users would prefer to be prompted for a password. E.g., if you
include the password in URL, then it shows in the open in the "Location"
field - and I *never* want to see my password on screen in the clear.