Screen Sharing gone mad:

This is what happens when you screen share from one machine, and then screen share back to the original:

The interesting part is that the farther back you go, the farther back in time you are, so it is much like the display of Time Machine itself, with the past receding into the background. As each screen refreshes, it carries its events backwards by one step.

This is the first time I have been able to get "Back to My Mac" working through all the various firewalls.