Everyone who's having issues sharing from your Mac, please make sure you go to your System Preferences on your Mac, then Sharing. Click the box next to "File Sharing" & also the one next to "Windows Sharing". Be sure to look under the options in that box & share your actual password protected user account or else it wont work.
If you're using Leopard or Snow Leopard, I think that "Windows Sharing" option doesnt have its own check box in the main sharing list in the system preferences & its buried under the regular "File Sharing" options. Just enable that & you'll be fine & will be streaming like a champ to your WD TV. (It may require a restart of your router, not sure).
Also, those wishing to connect from your Mac to the WD TV that you can see listed in the Finder under your shares cant do that because there's nothing to connect to. Remember, the WD TV doesnt have an internal hard drive, so just because the unit is listed there doesnt mean you can connect to it. There's nothing to connect to.
However, if you have a usb hard drive attached to the WD TV unit, that drive should show up & you should be able to connect & mount that drive on your Mac over the network. Then, you can copy files to it as well.
Lemme know how all this goes for you guys. But it should work & is very simple to enable. I think OS X oversimplifies things a lot & people tend to overlook options or think there's more to it than what there really is. But it totally works outta the box 100% with the WD TV.
P.S. Yes, it would be awesome if someone found a way to stream Hulu or Netflix from Mac to the WD TV & do it natively (screw using Parallels & doing it through Windows). That would make me a very happy nerd.
BTW, Mac users. Just an FYI, Orb is now available for Mac as well & works with the WD TV beautifully. What it does is stream out your iTunes & iPhoto library as a share so you can see it on your WD TV. I tried it & it works great. I was streaming my iTunes all day yesterday.