Facebook developers can create applications which run inside Facebook. For example, the Graffiti app adds a button to the New wall item popup, and has it's own pages inside Facebook.

What if we could do this also with StackApps? An example of an application which would run inside the trilogy, could be a pastebin. Hosted somewhere else, but has it's own canvasses on the trilogy (e.g. http://www.stackoverflow.com/apps/pastebin/new_pastebin and http://www.stackoverflow.com/apps/pastebin/pastebin/hi342ed ):

StackOverflow [Questions][Tags][Users][Badges][Unanswered] [Apps] [Ask Question]
                                                              ^^^^ Popup button
--------------------------------------------------------------------------------
Pastebin

-------------- Title: [                       ]
LATEST PASTES| Paste:
-------------| --------------------------------
- -  - - -   | |                              |
- - -  - -   | |                              |
-------------- |                              |
/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\
SO's footer Copyright etc... cc-wiki PEAK internet

In this example, the pastebin example app has it's canvas inside StackOverflow. The canvas is hosted on another site, let's say stackpastebin.com. It is written in HTML and embedded with an iFrame, or written in SAML (like FBML) and translated by the trilogy's system.

Everything is actually hosted on stackpastebin.com, but shown on http://www.stackoverflow.com/apps/pastebin/etc. Users can choose which apps they want to enable.

It would take much time to implement this, but I'm sure it would be awesome. What do you think?