Yes, there is a privacy setting that will prevent FriendCaster from being able to retrieve posts or other info from your friends if they have it enabled. Specifically, according to OneLouder's support site:
[I]t is possible that some of your friends have set their privacy
settings to block access to their profile, wall, photos and status
updates from third party apps like FriendCaster. This setting is
found in "Account --> Privacy Settings --> Apps and Websites".
In “Info accessible through your friends” you can see checkboxes for
the items that are available to apps. As an example, If your friend
has “My Photos” unchecked here, they won’t appear in FriendCaster.
Unfortunately Facebook has this restriction in place and unless your
friend allows third party apps we can't get around it at this time. If
your friends are using that setting, the info will only appear on