Writing to a Friends Facebook Wall/News Feed

Mar 12, 2009 at 6:06 AM
I'm pretty new to Facebook... and the Facebook ToolKit.

 The one thing that jumps out at me after reading a few posts is - What can you actually do if one of your users hasn't got any friends "installed" on your app?

 I have read that you can only write to another users wall/News Feed (is this correct term?) if that user has pretty much "approved" your app to let it.... Is this correct?

If that is true then is there any way of finding which of your logged on users friends has the app installed? i.e. Out of UserA's friends only X has in installed and Y and Z don't?

 I'm just trying to get my head around what is and isn't possible.... and how it all hangs together.