If you Google "US Customs block Canadian Man", you will read about one person's experience. Some points to note: 
* It appears the the US Customs will keep your email password in their database so don't forget to change it after
* The first time he tried to enter the US, he realized that because of content on his phone, there was little chance he would be allowed in so he asked to return to Canada. He tried to enter a month later and was refused because his phone was now too "clean". They want you to have lots of info on your phone to inspect
* Information deleted through the normal delete function on most phone operating systems can be recovered. 
* If Bill C-23 is approved by Parliament, a US border guard will have even more power during pre-clearance at a Canadian airport

To the article writer, how do you know the person that asked the question has an iphone. They asked about their cell phone. Are you saying that until you purchase an iphone, you don't have a cell phone?