Reports surfaced earlier today claim that Apple has changed its ranking algorithms for the App Store, shifting how applications make it to the top of the heap where they are more likely to pick up sales due to the extra visibility.

The change, which was picked up on by third-party analytics providers like Flurry last week and passed on to blog Inside Mobile Apps, is said to add other factors to an application's placement in the top sections of the App Store, besides raw download numbers alone.

Citing several applications that made dramatic jumps without a major update--including Facebook, Netflix, and Pandora--the report suggests Apple is now weighing how often applications are used (once downloaded) by daily and monthly users to better signify their ranking. Rival Google, the makers of the Android OS, and purveyors of the Android Market reportedly began the same practice earlier this month based on similar third-party findings.

Apple did not immediately respond to a request for comment.

While seemingly subtle, the move has a dramatic impact not just on games and applications, which depend on placement on Apple's list for new downloads and purchases but also the businesses that have sprung up to promote them. It could also provide more accuracy about what's hot at any given moment than downloads alone.

But that idea of apps effectively phoning home that data brings up concerns about what types of information Apple is tracking and using for listing and promotional purposes. This is at a time when Apple, Google, and app makers have been targeted by lawsuits for allegedly playing fast and loose with user privacy by allowing third-parties to track user activity.

To Apple's credit, the behavior necessary to track activity and send it back would still fall within the "collection and use of non-personal information" section found in the company's iTunes privacy policy:

The company also spells out its right to use cookies and other tracking technologies in various places, including "interactive applications," later on in the same document.

Race to the top Similar to search engine listings, getting to the top of Apple's list can bring great rewards. Applications that break into the top 25 lists can get a dramatic number of downloads and purchases, an effect that can snowball and push some higher and higher. The process can also be beneficial to developers who produce "lite," and iPad versions of their applications, where visibility can push the application's counterpart to the top as well.

Developer 2-D Boy, the makers of the World of Goo application, which currently sits inside the top 15 iPhone apps and in the top 30 for iPad, noted in February that nabbing the No. 1 spot on the charts provided sales that were orders of magnitude higher than No. 2. At the same time, the developer noted that the glory could be short-lived:

That postmortem also noted that the same application, once it fell outside of the top 10, was still receiving a high amount of exposure from users.

To back up 2-D Boy's claims, applications like Rovio's Angry Birds series have managed to stay on the top of the curve, raking in sales month after month and hanging on to the top spot. But even there there's a chance to be knocked off by new challengers. Andreas Illiger's Tiny Wings, for instance, dethroned longtime chart topper Angry Birds earlier this year and has managed to stay in the top 5.

The business of promotion What makes any under-the-hood changes of special interest is the business that's cropped up around promoting applications. Solutions like Flurry's AppCircle program and similar efforts from TapJoy and W3i give developers a way to boost downloads of applications in exchange for ad space within their applications, or a payments per installation. When done as part of a large promotion, such campaigns can push applications out of obscurity and onto the charts where they can begin to gain downloads and users organically.

How big are these networks In an announcement about its new self-publishing program last month, TapJoy said it had more than 200 million mobile customers and 100 million social gamers who could drive downloads to the point of being able "to ensure that a game becomes a top hit." That same program could end up being less effective in the long run if the usage of that application is part of the ranking, quickly pushing off applications that pulled in big download numbers but failed to keep people using them.

Apple also has what can be called a "tepid" relationship with the analytics and advertising arms of such networks, including Flurry. In early 2010, ahead of the iPad's official unveiling, the company shared identifying details about Apple's then-unreleased tablet, including what kinds of applications Apple was testing and the version of iOS it was running. All of this was based on system data Flurry was grabbing from applications that were making use of its analytics technology and being tested within Apple's walls. As a result, Apple changed the rules of its software development kit to keep analytics from grabbing device data.

Coming back to the rankings issue though, the bottom line is that there's still very little proof outside of some out-of-character rank jumping to point that there has been an overwhelming shift in how much it takes for an application to get on and stay on the list. Just like any other ranking algorithm, there are factors in play that determine the scale and speed of those jumps. The real question remains what else is a part of the mix that determines what takes an app to the top, and if Apple is trying to keep that a moving target.