Is the firewall enabled in Mac OS X by default, or not?
I just bought a new MacBook, as I'm stepping down from owning a Pro and moving to a MacBook/iMac setup (more on that later), and I noticed something a little disconcerting: after going through the generic setup out of the box, Mac OS X's firewall was not enabled by default. I didn't fiddle with any settings during the initial boot and setup (besides entering a password for my wifi network and my .Mac credentials - about the only settings you can fiddle with), and I spotted this strange quirk in the Sharing Preference Pane when going to name my machine before the initial .Mac sync.
What gives? Is Mac OS X 10.4's firewall enabled by default or not? I honestly don't remember which exact version of 10.4 this MacBook shipped with (I ran Software Update immediately on startup and only caught this firewall quirk after the restart), and I'm certainly not some certified, 6-figure security expert - I'm only reporting what I saw with this initial setup.
So does anyone know what's going on? Discussions about Mac OS X's (and 10.4 specifically) inherent security often cite the firewall being turned on by default - though that clearly wasn't the case with this machine. What say you, TUAW readers?