sudo echo '10.0.0.1    local.freebsdonline.com       local' >> /etc/hosts
cannot create /etc/hosts: Permission denied

Or if you need to run shell commands, say a simple change directory:

 $ pwd
/home
$ sudo cd /usr
$ pwd
/home

The command goes without an error buf after the command runs you realize that it did not work. 

This is due to the fact that you are trying to gain rigths for a shell that is alread started.

The workaround for this is to run the commands in a sub-shell like this: