Samba networking, needs password or not?

[Giorgos]

I have set a directory to be shared in my samba server and I was trying
to access it from another ubuntu box on the network. It was asking for a
password, I gave my ubuntu password but it wouldn't accept it. In
#ubuntu I found out that you have to create a user and assign him a
password with smbpasswd. But another user told me that he had the same
problem and he mapped a drive directly using \\192.168.0.x/sharename (or
something) and it worked without password. 

Isn't this insecure? What was the point in asking for a password in the
first place?