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I don't see a very good long term strategy towards ranking three dollar articles. At the very least, you'd need really high quality content, or you have to find a way to be way useful to your users. Or both.
You should concentrate on quality, not quantity.
User interaction = programmatically measurable
Quality = subjective, not easily measurable
I wish this were true. Yes we all hear it all the time but as was illustrated by EditorialGuy. Huffpo has some of the worst content yet Google loves it.
Which is empirically better - in depth, knowledge content that only a small percentage of people are ever interested in, read through or share, or more generic content with less depth that goes viral and gets thousands and thousands of pageviews and shares?