A Wired blog on the effect of Half Life 2 - Episode 1 on the market.
The idea is certainly not new but prehaps its time is right, we all have fast enough pipes to download 100MB chunks without too much thought. Prehaps more exciting than the Valves of the world getting you to pay for HL2 a dozen times, its that must smaller developers can get a kick start.
Its really not hard to get a basic game engine together, the problem is usually that its takes a while (and a fair bit of cash) to develop 20 hours of gameplay and assets. Once you take off the constant of the base game/engine it takes 1/4 of the time to develop 5 hours of gameplay. The first episode will be the most expensive to develop cos you have to have developed the constant but future episodes will be much cheaper and that helps because it means you can start earning revenue much sooner.
Its an interesting idea, that certainly something I’m and several other peeps I know are seriously looking at for the future.