Your Facebook “private” friends lists are no long “private”… according to FB…
“The people on the list you’ve shared with will be able to see each others’ names. This gives them more context. For example, if I see that a post is shared with my five closest friends, I am much more likely to comment freely on it than I would be if I didn’t know who else could see the post.”
Here is the full article: http://blog.facebook.com/blog.php?post=10150278932602131
Here is a link to make a suggestion to FB (you must be logged into FB):
Don’t get me wrong, I LOVE the new lists, they are a long time coming in helping users control and limit who can see their information and content (posts/status updates). HOWEVER, consider this: Have you ever used the bcc: feature of your email? Most people use it now to limit the amount of SPAM but that is still a good reason to use it. What if your email client suddenly decided that everyone on your bcc: could see to whom else you sent that email? That is what FB has done, they have now allowed people on your custom lists to see all the names of everyone that you have allowed to see that post. If that privacy setting was important to you, then you will want to take note that your list membership is no longer private.