I know about the Safari captcha system (the only one of those that's truly analogous to WEI). Nobody cared about it because Safari's market share is very small. I would care if those companies jumped on the Google proposal because Google has the market share to force this through and make it ubiquitous, which is why I was wondering whether those companies had come out in support of this specific proposal. If they had/will, that would make WEI totally inevitable.