I'd love to see page-internal isolation functionality: basically, a better Caja. Let me designate part of the page as untrusted by the rest of the page. What

I'd love to see page-internal isolation functionality: basically, a better Caja. Let me designate part of the page as untrusted by the rest of the page. What if a web-specific StackOverflow-like site could (securely) display arbitrary examples? What if a social network status update could contain live code, but that code couldn't break out of the update?