Right way to handle friend-multi-select post on facebook, issues with session

Question

1. Do I need a infinite key with fbml facebook app that resides on fanpage?

2. I am asking user to select user and posting it(facebook posts) to my server. On my server I want to get user_id and selected friends Id. Everything is fine with selected friend_ids, but have issues with getting id of a user. sometimes I can get it all fine, sometimes I am getting session expired exception, sometimes I get nothing. any ideas why this is happening?

Answer 1

As far as I stumbled, my issue was because I didn't ask a user for special permit, though I didn't tested it. In the projects I took different approach and just prepended encoded get var to url that we can set for request form in facebook