Plan 9 provides a great infrastructure for sharing resources including interfaces to interactive applications (such as windows in rio and ACME). Developing a more complete interface to these sharing facilities would promote their use in daily activites. Combining these extensions with Cross domain authentication may allow greater collaboration between the now widely distributed developer community.
There are a number of topics and ideas in this area amounting to how to share, when to share, levels of trust, levels of respect, etc. I'll do my best to fill out this page with my ideas as time permits.