Turn it on the hover over someones formatname output in CB Activity and several other locations. It looks like the below.
It's undocumented and no blog about it at this time as it's still being improved. I'll be improving the mini-canvas styling in a later build and for CB 2.2. You can substitute in additional content to replace the online status and name output but that'll be changed later to where it substitutes under the name as seen in full size profile canvas view.
krileon
