If I remember correctly:
When the FAQ was established it was the editors depot's staffs responsibility to transfer solved topics to the FAQ.
After a while the responsibility was gently suggested to be on everyone in the staff.
And finally it was decided that anyone, even members, should be able to add to the FAQ, but when adding the entry goes as pending and an editors depot staffer needs to check it and unpend it.
Now, if I look at the pending FAQ entry list, it seems that members are indeed able to add an entry (there's some silly looking pending FAQ's in there). I'm thinking that snYpir has made a post about it in here somewhere.. can't remember exactly, so be critical to this post