The switch in itself is not the issue, routers have inbuilt switches, it's just that with a basic switch you'll need to set up a workstation as your router and if that's a windows firewall/ics based setup, then it get's risky, security wise. When it comes down to just two pc's connected via a usb modem, or a cable modem connected via a second ethernet port, the switch is completely redundant anyway as no switching will occur (in this case only crossover cable is needed).