sudo free-for-all

[anthony baldwin]

Could someone pelase explain to me why every user I have added
to my system has access to sudo, when I have not added them
to admin, sudo or root?  Nor have I added sudo, admin or root to their 
accounts.
How do I disable this?
And, why is it that every user on the system can access everyone else´s 
/home?  Shouldn´t each individual´s /home only be accessible to that 
particular user?
I thought security was supposed to be better with sudo, or something, 
but I´m not seeing that.  I mean, I suppose perhaps from outside the 
system, I don´t know, but within it, it´s a free-for-all.

I want to be the only user on the system with sudo, and I don´t want 
anyone to be able to access my /home, or anyone else´s, besides their 
own (like I had it in Fedora...well, okay,
I was the only with root, not sudo, but you get the idea)...

tony