I have Craft Pro (2.1.2564) and cannot locate the "share" functionality outlined below. When I edit an entry, The Live Preview button in Chrome (OSX) has only the Live Preview button with the eye icon and then an arrow. That row triggers the Live preview and not any sharing function.

http://buildwithcraft.com/updates#build2554

Added a “Share” button next to entries’ Live Preview button, which opens the current entry/draft/version on the front end, with a tokened URL that can be shared with others without requiring them to be logged in.