I have custom filters available for all sorts of various groups, such as close friends, people serving in Iraq, etc. Yet, when I do a search for all recent LJ posts out of Iraq, I see recent posts from friends listed there that aren't showing up in the custom friends list, even though I've checked to make sure they are part of my custom group.
Now, I have a huge friends list, but still, how hard is this to really test? I suspect it effects some accounts more often than others, but that's really just a feeling.
So, just in case you feel that you don't get a lot of comments from me lately, there might be a reason...