Its a good thing that Apple is sourcing multiple channels for its components. Recently they went with Japanese manufacturer of memory called "Elpida". They were under loss and the recent Apple order boosted their revenue while giving Samsung the boot.
When you are designing your products with a competitor the competitor sure walks away with a ocean of knowledge. Say what you may about not compete agreements or other legal paperwork, the knowledge is still there, which is more valuable than money.
Sony under Howard Stringer made this mistake by trying to outsource LCD panels from Samsung. I am glad that plan has been put to rest, too.
I used to work for a giant automotive manufacturer and they always had multiple suppliers for their parts. If one supplier had issues they will supplement it with the other supplier and keep the lines running... While there are others who choose a single supplier .. advantage being cost.
The 13" retina macbook pro has a article by a chinese blogger who says "Tim Cook does business different than Steve Jobs. Tim Cook has solely decided to give the whole contract to Foxconn and they are having issues with the new glue used to stick the iMac glass with the lcd panel. So expect delays...."
Too many cooks can spoil the food, but in this case looks like a case of one Cook, spoiling the iMac release date by relying on one supplier.
Who knows if any of this is true? Thats why we call it MacRumors right?