All this data is based upon research by Gartner, who claims that, should sale trends continue, Apple could retain 2/3 of the paid mobile app market into 2010 (amidst growing competition from Android, Palm, RIM, etc). Of course, if Apple releases an app-wielding tablet, market share could error greatly in their favor again.
(Note: there's some discrepancy in these numbers, as Engadget counters ars' 99.4% number crunching with a 97.5%. Whatever, either way, it's enough of the market to mean every other retailer was moot in 2009.)[Ars and Gartner]