When the App Store first launched in July 2008 anybody could review any application. No purchase was required at that time. This led to many critical reviews especially from people not happy with having to pay for applications.
In September 2008 Apple changed the system allowing only customers to leave reviews on applications they had actually purchased and downloaded.
Now it appears that Apple has removed these initial non-customer reviews from the database entirely. SEGA's Super Monkey Ball count dropped from 4197 reviews down to 3710 while Namco's Pac Man dropped from 395 to 122.