I think there's a big potential for a commercial product here. Couldn't all of the security and privacy issues be addressed by just buying a bunch of hardware, setting up the VMs and then selling testing time?

Rather than fully distributed make it more (pardon the buzz word) cloud-like?

With the amount of javascript being written these days, I think the instant testing infrastructure with zero maintenance would be a huge sell for small and medium size companies.

edit: Although, for that matter if you're going to own the hardware/configuration, you could just as well go with Selenium and sell time on that. Either way, I think people would buy time on either sort of a setup.