I've been wondering that about webOS. I've started making a few apps that fill my own personal wants for the platform; and it seems that in the short-term it's a platform primed for opportunistic development.
Hundreds of thousands of consumers have recently gotten their hands on a Touchpad, and the HP store has so little new content coming into it that competition is pretty much non-existent. There are also plenty of gaps that are entirely unexploited by existing apps that haven't been found in iOS/Android since they launched.
The first two are so much nicer to develop for due to tooling, webOS is pretty nice but perhaps a dead end!