"After hanging out around the #6 top rated slot for a month or two, our game's rating started to drop very quickly," Cthulu Saves the World dev Robert Boyd wrote on Microsoft's App Hub Forums. "In less than a week, we went from being #6 top rated to our current spot of #11." And how are the lacrosse games doing? "In contrast, the Lacrosse games which were in the middle of top 20 best rated (I don't remember the exact positions) are now ranked #4 & #5," Boyd observed.
For its part, Microsoft's XNA Creator's Club has acknowledged the possibility of manipulation, tweeting, "We are investigating a possible misuse of ratings on #XBLIG titles. We'll announce more information here as it develops."
The real issue is how easy it is for a group of individuals (take the 177K fans of College Lacrosse's Facebook page) to influence the popularity of games on the service: Users can rate games on Microsoft's website without owning an Xbox, purchasing a game, or even playing a demo. When download numbers are as tied to rankings as they are on the Indie Games marketplace (just like on the iOS and Android marketplaces) this issue is really critical in maintaining the fairness of that ecosystem.