This is an example of a web page that contains an Flash video player and uses AddThis for sharing, using only Client API parameters and not any special page tags. Play with it, view the source, and read the overview of sharing widgets with AddThis.
This is a YouTube Flash player embedded with a simple object tag:
By passing certain parameters to the Client API, this page tells AddThis the URL, height, and width of the Flash object to share (as configuration properties). View the source of this page to see the actual call, and share this page to iGoogle to see it in action: