I own 2 macbooks, iPhone 4S, iPad 3 and I had iPod Video (battery dead, but should work otherwise). Every iDevice had broken cable after about 1 year. One macbook have broken cable. Other macbook have broken cable, but it still work, not sure, how long. I started to apply pen springs to the cables, it seems to help a little bit.

I'm sure that it's intentional design, so Apple can sell more of their ridiculously priced accessories. Integrated chips in their accessories, making them harder to replicate, seems to approve that hypothesis.