The problem with the article isn't what he is saying - it is the way in which he is saying it and the way in which he has selectively chosen certain information both from a confidential email conversation with myself and from pieces of sales data on the site to paint a bad picture of the site.
We all know that data gets adjusted from time to time for a variety of reasons. We all know that vgchartz is a team of amateur enthusiasts doing their best (whilst doing paid jobs / college courses) to provide a free source of estimated sales data. Picking a couple of (poor) examples to show that we don't always agree 100% with NPD is hardly new. We have a lot of trouble tracking the sales of casual titles as do NPD actually - back to the Walmart thing again and just how you estimate for such a huge chunk of the market.
But anyway, personally I am annoyed that this guy approached me for an interview under the understanding of writing an article about vgchartz and ends up using it to unfairly bash the site and twist things around.
Pretty unprofessional if you ask me.