Hope_Fowl - 3:09 pm on Jul 12, 2012 (gmt 0)
The Knowledge Graph shows us that Google is collecting semantic data. We should not be surprised if they're trying to figure out who is authoritative based on the concepts presented on a site, rather than mere text. Google might be figuring out that your site is presenting the ideas first, and the others are echoing them with different words. Or maybe your site is authoritative due to the large number of concepts related to its field, while the copiers are picking away at smaller subsets.
Your traffic increases could be due to Google using the other site's activity as an indicator of interest in your topic, so the ranking of your article might be pulled upward along with the rewriter's material.