Excellent piece! I am bookmarking this one to share in other forums when trying to clear up some of the confusion surrounding AncestryDNA results, what they mean, and what to do with them.
I would add: The list of shared surnames has no significance other than the fact the surnames appear in the direct lines, in the first 10 gens, in both users trees. It is ancestry's way of saying "Hey, you share dna with this person and you both have these names in your paper trees. You might want to check that out for a *possible* connection." Your match is to the other user and was based on dna. The interface that displays your match's tree data is simply a tool that that allows you to more easily compare that data. There is nothing presented there - other than the predicted relationship and confidence level - that is based on dna, (including leaf hints to a common ancestor in both trees).