It's not that people don't want to live in rural areas, on the contrary most people would probably like to. It's just that there aren't any jobs in rural areas, and ultimately putting food on the table is what matters.

Well, any given rural area of the same size. America only recently crossed the 50% urban threshold.

Hmm, I suppose it depends on how you defined "urban," and the particular area (etc), but a quick google generates a lot of results that show the U.S. generally passing the 50%-urban threshold around 1910-1920...

E.g. the graph here seems typical: http://blogs.census.gov/2012/04/04/how-do-we-measure-urban-a...

That's a pretty flippant statement, just like the one in the main article. When did having fewer people make it junk/worthless?

Rural/urban is a function of density, not quantity. In a lot of places, the distribution of people that live in urban and rural areas has been about 50/50. If the distribution tips more towards urban, than that might be an argument.