Is it possible to post on friend's wall using the standard feed dialog or I have to create my own dialog for this?
UPDATE:
I know that it is possible to post to a friend's wall directly using requestWithGraphPath. But I'm trying to figure out if I can use the facebook dialog for this. For example Draw Something seems to be doing just that (see screenshot below). However, I tried sending 'target_id' as well as 'to' and neither works. Does anybody know how to do that?
I found the solution. Just add "to" parameter with ID of the user you want to post to. I tested it works.
UPDATED ANSWER :
facebook annaunced that by 6.06.2013 it will not be possbile to post a friends wall via GraphAPI
https://developers.facebook.com/roadmap/#february-2013
Removing ability to post to friends walls via Graph API We will remove the ability to post to a user's friends' walls via the Graph API. Specifically, posts against [user_id]/feed where [user_id] is different from the session user, or stream.publish calls where the target_id user is different from the session user, will fail. If you want to allow people to post to their friends' timelines, invoke the feed dialog. Stories that include friends via user mentions tagging or action tagging will show up on the friend’s timeline (assuming the friend approves the tag). For more info, see this blog post.
This seems to be a very similar to iOS Development: How can I get a Facebook wall post to show in the friend's news feed?
Maybe that will help, as I think @kgutteridge has the right answer.