While it does suck that all of Apple's chargers fray so easily, however I don't see it as a reason to be cynical about their products. In this case, Apple seems to be prioritizing environmental friendliness over function here. The cables are so weak because they have specifically removed PVC from their charging cables.
> The greatest environmental challenge facing the computer industry today is the presence of arsenic, brominated flame retardants (BFRs), mercury, phthalates, and polyvinyl chloride (PVC) in products. Apple engineers have worked hard to eliminate BFRs and PVC from MacBook Pro circuit boards, internal and external cables, connectors, insulators, adhesives, and more.
That cable has an external insulation, which is the weird rubbery stuff that frays. The internal wires are also insulated. What are they insulated with?
By mixing different types of insulation Apple have just made it harder for people to reclaim and recycle the PVC. Recycling the PVC is possible because people scavenge the copper wire.
http://www.apple.com/macbook-pro/environment/
> The greatest environmental challenge facing the computer industry today is the presence of arsenic, brominated flame retardants (BFRs), mercury, phthalates, and polyvinyl chloride (PVC) in products. Apple engineers have worked hard to eliminate BFRs and PVC from MacBook Pro circuit boards, internal and external cables, connectors, insulators, adhesives, and more.