This is the dream of Bryan Lunduke, formally of the Linux Action Show. He famously vented his frustration on one episode, fed up with Google not releasing Honeycomb code, Nokia pulling the rug out from MeeGo, spyware and malware being installed by handset vendors and carriers, censoring of app stores, etc. He desperately wanted a phone that was really open, that people could hack, and that would let him run standard open-source software without spyware, censorship, dependence on proprietary bits, etc. Something that could live on even if a corporation stopped supporting it.
Lots of viewers expressed the same views and a working group was formed to create just such a project only a few months ago, and has been sorting out technologies to base it on, design decisions, etc. WebOS has just fallen into their laps! The community will take this and run with it, and it'll be an anti-mobile OS! It won't be something you get from a vendor... it'll be something you'll put on the phone yourself! Fully open, no backdoors, no spyware, no malware, no censorship, no crippling of functions... nothing to get between you and using your mobile device as you see fit. Just like Linux, you'll point the package manager to whatever repositories you want to get your software from... no app store lock-in. From walled garden to wild west, it'll be up to you. You'll be able to pick your phone, pick your carrier, and then install your OS... no more "exclusives".
No, this is going to shake up the trend towards locking down devices, dictating specs to phone designers, etc. that even Google seems headed down. It's going to be quite a disruptive force, and it's going to be quite a show to watch.
As for developers... if Linux gets along just fine with only a small number of commercial vendors, WebOS will be just fine, especially given that it can quite easily port *real* software over from the Linux world. While other users were showing off fart apps, Nokia N900 users were using SSH tunnels for VPN, kismet for passive wireless network monitoring, controlling their home PCs over VNC, etc.
WebOS is going to have both passionate and hard-core open-source developers writing for it and has nothing to worry about in that regard. 
