I was looking at Silence of the Lambs and trying to see what made it good. What I think made it good was primarily the execution. (Manhunter had the same basic concept and was pretty awful). But it can't be good or bad until after it's chosen in the first place, so I see your point about smooshing.
So there's really two targets to keep an eye on. There's the question of, "Why are we choosing this source material?" (Which is the market-driven, concept- driven, etc. lesson from the earlier column) And then there's the question of, "How do we best adapt the source material for our purposes?" (which is the "finding the focus/theme/etc. lesson from this column)