When something is broken, it's not going to get fixed whilst you ignore the problem or make excuses for it. The sales numbers on this site are abominably poor, particularly around the holidays. Sorry, but that is a fact.
ioi can say that the figures are generally within 5% and therefore acceptable, but that is rarely true for the figures provided. Sure, if you look at the cumulative sales (which are regularly adjusted on this site every time the quarterly results get posted by the respective company) now that the Wii, 360 and PS3 have all sold 80million plus, the results may well fall within the 5% error ioi uses in his argument. However, if you look at the numbers on a weekly basis, VGChartz has a very poor track record. If the site was any good at forecasting, we wouldn't be seeing these large adjustments (relative to the quarterly sales). Either the sample being used is unreliable, too small to be representative or both.
ioi deserves a lot of praise for making this site the success it is with a large (and I presume growing) following but the site does need to get better at the sales tracking/forecasting. If it did, I'm sure Sony, Microsoft, Nintendo and many of the big publishers would take it more seriously and ioi would probably be able to reap greater rewards for the extra work that would be involved.