Someone who would want to sell phone management services to third parties. You could set this up to accept payments to create accounts, which give you credits with which you can buy phone numbers and accept calls, design phone flows, etc. Basically a Grasshopper-like service.
One thing that I couldn't understand from the openvbx documentation was how it fit in with the phonelines in your business. How would a business with a PBX with 30 extensions replace the PBX with openvbx?
Would the employees only be able to call through a browser or is there something else available?
Employees can call out through the browser and receive calls through the browser as well, or forward their extension to a different physical phone number to pick up. In fact, the default action is to forward to a phone number or take a voicemail if you choose to not accept calls online via the browser.