ah i see
The reason for the difference is:
Apple requires all iphone apps to be scrutinized and approved by Apple. So it can take months for a new app to get published for iphone. Ergo; folks release unofficial apps for iphone that require a "jailbroken" phone to use
Android on the other hand allows developers to add apps to the Market as they wish (with some decency restrictions i believe). Ergo; an underground app environment is not needed for android.

