What you're looking for is Facebook's Open Graph which, when authorized, can post to a user's timeline through "frictionless" sharing. The is not to post without the user's involvement however but many have skirted that line frustrating users and leading to poor response rates and as a result Facebook responded last week with an announced set of changes. The biggest shift seems to be in requiring apps that share only through "consumption" [rather than action] to use built in actions which, as lets facebook aggregate, filter and suppress down what doesn't perform.
Simply put sharing should be tied to intent. Unless it's extremely obvious that you will share on view, and worthwhile, you're not going to survive the user.