You can find more information about the setup of EPSON parallel port scanners on Christian Bucher's web site.
It is necessary to run the frontend as "root" user when a parallel port scanner will be accessed. The reason for this is that the IO ports that the backend has to control can only be accessed as "root".
It is not neccessary to actually run the frontend as root, there are two ways this can be avoided:
chown root xscanimage chmod 4755 xscanimage
I would however not recommend this because it causes another security problem. Do this only is you are not very concerned about the security of your system (e.g. you are the only user, it is not connected to a network, you like to walk a high rope without a net)
Please read the saned man page for more information about how to setup the net backend. Even though the man page discourages to use 'root' as user ID, in this case you have to do it, otherwise the backend will not be able to access the scanner.