Applying game dynamics to virtual worlds

Jeremy Liew has an excellent post up today - Applying game dynamics to virtual worlds. Especially this passage:

4. Free to play can mean casual (to start) but if you want to get paid, you have to focus on the hard core. They are the ones who will shell out real dollars for digital goods. There must be a satisfying hardcore experience even for casual and social games. Not only are they the sources of your revenue, they are also evangelists, and beacons on the horizon for new players. If you’re missing hard core, you’re missing deep fun. [THIS WAS A LIGHTBULB MOMENT FOR ME].

I've seen this lesson unfold in practice -- it's TRICKY, you have to design an experience that's light enough to attract massive numbers of casual players, but deep enough to attract the get-a-life Web gamers who have the time and propensity to get deeply involved in something.