I suppose a better way to state it is that it IS Apple's fault since they changed the way the iPods work so they no longer work with those third party accessories. But it ISN'T their responsibility to ensure changes they make in their product line are backwards compatible with the thousands (neglecting passive ones like cases) of third party accessories available on the market.
But while they don't need to ensure backwards compatibility or even care if third party stuff works, it is in their best interested to try and do so simply from the marketing and public relations aspect. People who updated from, for example, a 4th generation iPod to a Classic only to find the Classic doesn't work with the several hundred dollars (or more) of accessories they already own, are more likely to return the new Classic and stick with what they had before or at best buy a discounted 5th generation model. But in either case, their attitude won't be to buy new Apple products or replace their accessories but instead to just use what they have until it dies and then see what the alternatives are what that time comes.
In other words, the slam dunk sale Apple had with an upgrade iPod for those users no longer is the slam dunk and in fact might prompt them to look at other brands or solutions (e.g. Car stereo replacement with a built in hard drive and MP3 player vs. an iPod dock for the car).
Patrick
