Should Married Couples Share Their Login Passwords To Website

I know when two people marry they should (or usually) becomes one. but does this mean they will totally lose their privacy even to the smallest bit, I mean things like phone lock code, bank logins and other very personal info, do you think these should be shared amongst couple? given that some personal message could be going into the facebook or so, is it a wise approach to share these passwords with your husband/wife? or its better to be smart about these things, marriage or no marriage