I've encountered an issue with the friends/ids where the IDs returned can contain IDs of non-existent users. One example of this can be found when getting the friends of the user id = 16067667 (http:// api.twitter.com/1/friends/ids.xml?id=16067667). Within the IDs returned, there is a value = 28745723, which can not be found when using users/show (http://api.twitter.com/1/users/show.xml? id=28745723).
Has anyone else encountered the same bug when using the friends/ids or followers/ids endpoints?