The issue this raises is one of prerequisites... are things like accelerometers supported on all Win8 machines? What about cameras?
For example, some apps require a gyroscope, which I think handsets only came out with in the second generation. If you try to install one of these apps in the store, you'll be warned that some functionality won't work (or perhaps won't work at all - I haven't seen this). Similarly, I've seen reports that in the upcoming update aimed at lower end handsets, there'll be warnings in the store for the few apps that don't work with limited ram requirements.
I would predict Windows 8 will keep a similar list of the device's capabilities and warn the user in the store if they try to buy something that won't work.
I was wondering though if there are any apps (or if developers have the option to set this) where an optional device feature such as the gyro is so integral to the app that it won't even install without the device capability. This is what I haven't seen yet - though maybe the marketplace is already filtering them out for me.