Note that both Chrome and IE have been blocking this for some time now. IE did it first.
It seems like Chrome really forced the ecosystem to move towards auto-updates and sandboxing. Each of those have transition impacts for developers and publishers.
Mixed content though, I've got to imagine that's a hard area for Google to lead on, since its transition challenges primarily affect ad integration.
This follows on the heels of the "disable third party cookies by default" row. I'm wondering if a) Google's business interests will prevent them from being a first mover on security and privacy in browser development, and b) if other browsers will start exploring these issues just to force Chrome to make hard choices.
My main dev environment is FireFox and i hate it when things work for FF but not Chrome.