network topology question

[stonelx <mike@stonelx.ath.cx>]

Hi all,
I was wondering if anyone thinks this would be
bad networking practice:

To setup a linux box with 2 nics.
One with a public IP and the other with a private IP.
The linux box is acting as a masqurading box. (ipmasq)
However, both nics are plugged into the same switch or hub.

Basically, you could be running 2 different subnets
on one network segment. Some machines off the switch would
have public IP's, and some would have Private. 
I understand this could cause all kinds of havoc if file services
were running on the linux box. (netatalk, samba) but lets assume
that the workstations in this Lan are for internet surfing.

Anyone out there tried this and have any experiences to share?

Thanks
Mike