I'm not using Adblock or anything similar (I'm on Safari 4.0.2 on Mac, btw).

I see some code related to google ads in the source but they're not showing on the page.

Maybe the code is just a placeholder.

It shows up for me. (OS X 10.5.7, FF 3.5)

Now I see them too.

It usually takes a view or two for the ad network to "learn" you. This usually happens with smaller networks though, google should know who you are by now (assuming you have been to other adsense enabled sites.)