i thought it was already pretty clear that Apple disabled a lot of features of iOS4 on older devices. not sure if that is the case is with iOS5 as well. of course siri is not included in iOS5. that is another disabled feature on older devices. and it is disabled even on iPhone 4 and iPad 2 for god sake. both of these are fairly powerful devices. and not even one year old. i would imagine that it would be possible for mobile manufacturers to deliver feature limited updates of Android on older devices. it's not like the system requirement goes up with every update. on the other hand, android probably becomes more efficient with every update.