Yeah.. now that we support explicitly shared actions, we'll be looking into some way to add a popup or checkbox to some actions inside components to check if the user wants it posted. That will be very difficult though to support all the different components and, also, since the user would have to opt-in, the amount of sharing would go down.. which is really what Facebook wants. They want less, higher quality, higher awareness shares when possible.
The other option, of course, is to create an "I uploaded this" button that the user can explicitly share the action on their own. For a photo, especially, that provides the benefit that the user can add a message and tag a place and people as well.
Hope that helps,
Alex