Most Hollywood celebrities seem to use an iPhone, with Apple's flagship being so popular that even those Samsung teams up to market its products are often caught tweeting from an iPhone. But there are some, like Jay Z, Martha Stewart, and Dana Brunetti, who have switched to a Samsung phone and haven't gone back to the company's biggest competitor. Why? Well, these celebrities didn't go online or to a mobile store and choose a Samsung over the iPhone; instead, they were converted into Samsung users thanks to a Samsung program called “White Glove.”
White Glove is a marketing effort that Samsung has been using to convert Apple-using celebrities and influencers and get them to start using Samsung devices. The company will often send someone over to a celebrity, sit down with him/her and talk them through how the device works, and then leave the device with them as a free gift. In the case of Dana Brunetti, this resulted in him keeping both the Galaxy S III and the iPhone with him for a month of use, after which he put down the latter and started sticking with his S III, a device he says has many useful features that make his work easier, including widgets.
It's a pretty interesting program that Samsung has going, and the source article goes into detail of what makes it tick, letting the Korean manufacturer take away at least some high-profile celebrities away from the iPhone, so go ahead and give it a read.