VGChartz providing the mirth

Solid hardware and software sales figures are hard to come by for any machine or game, but website VGChartz claims to have the most accurate figures due to several scientific methods including surveying gamers, statistical trend-fitting and studying resale prices to estimate supply and demand. How accurate are these figures? Microsoft's Aaron Greenberg finds them laughable:

LOL’ing at sales reports from VGChartz, why do people release info as official when there is no source or science behind the#s?

We'll surely receive official sales data from Microsoft in the near future, the contents of which hopefully won't be so laughable.