Firewall in a virtual machine?

[bs_texas]

Just curious what you security/networking type people would think of a machine with Windows 2000 and vmware on it running a linux based firewall, like SmoothWall or a linux version of CheckPoint, on that machine within a vmware virtual machine.

Or even... having a linux machine with vmware for linux on it running a firewall in a virtual machine?

Would that be doable, or wise, or secure, or whatever?

(I know somebody may post something like "why do that? why not just use iptables?" or some such... but that's not the question.)

Thanks...