Samsung is a very unique company. They're one of the few players in the mobile industry who not only make mobile phones, but also manufacture many of the components that go inside their devices. Take the Galaxy S III for example. It has a Samsung made display, a Samsung designed Exynos processor, the RAM inside is definitely made by Samsung, and so are the storage chips. People often wonder how Samsung can make such advanced devices. Well, there's your answer. They make the advanced components that are required to build bleeding edge smartphones.
HTC, like many other companies, relies on Samsung for parts. According to DigiTimes, the Taiwanese handset vendor is in the process of transitioning away from using Samsung components. Specifically, they're now sourcing camera sensors from OmniVision and Sony, and screens from AU Optronics. Does this mean HTC has ceased doing business with Samsung? Not in the slightest. They're just dabbling with other vendors in order to protect themselves. You know the old saying “don't put all your eggs in one basket”? That's what's happening here.
Now don't be fooled, this isn't just an HTC only move. Apple was one of the first companies to do this. Considering that Samsung is their number one competitor, that shouldn't surprise you. Also, we all know about Apple's ongoing legal battles with Samsung. It's kind of difficult to maintain a business relationship with a company that you're also dragging into multiple courts in multiple countries.
Will other companies start mimicking Apple and HTC and wean themselves off the Samsung tit? It's hard to say at this point. Part of the reason why people love dealing with Samsung is the fact that they don't have to deal with multiple vendors. Think of it like this, would you rather go to that one grocery store that has everything you need, or one store for milk, another for bread, yet another for vegetables, and then on your way home you stop by the butcher?