The transition to head-worn mobile computing faces significant barriers. Unlike the smart phone, this requires big changes in behavior. As the author points out, people already had phones — and blackberries. While smart glasses will make what we’re already doing (e.g. mapping, messaging, photography, social media) better, they are a new idea. In order to get people to buy Pepsi, they have to know what soda is. For this reason, adoption may look more like personal computers, which took fifteen years, than tablets, which took two years. This is because these new technologies represent a far greater disruption. It will take longer, but it could also be much bigger.