Again, if Sony chose to recognize the revenue of the PSP over a certain period of time (like Apple does with the iPhone and AppleTV) instead of as a lump-sum at the time you purchase it (like Apple does with the iPod touch), then they'd be able to add major, new functionality without charging.Sony did not charge me for any sort of update.
The best case you have is to argue that Apple was stupid for not thinking ahead that they'd be adding major, new functionality to the iPod touch.
Were you not around 6 months ago when Steve Jobs was adamant that there'd be no native applications; web-apps were as good as it was going to get? The accounting that they used to setup the iPod touch is totally consistent with that, no?