How do you handle these? I personally hate to use them unless I'm running some sort of mystery plot and some integral clue is held in something not commonly known, but then on live-play podcasts from other GM's I'll hear them ask the group to roll a Lore [Xenos] roll to see if they know the name of that big, green hulking creature in front of them screaming "WAAAAAAAAAAAAAGGGHHH!".
That, to me, seems like a waste of time and effort.