The following url will display a list of the user's friends that use the given app:
where XXXXXXXXXXXXX is the id of the given app (any app id, not necessarily my own app).
This such url is found when looking at the app's profile page under the section of "Friends that use this app".
What I want to know is how can we get a similar list of ALL the given app's users or at the very least, the friends of the user's friends that use the given app?
For example, how could we see a list of all players that play FarmVille?