Gateway to a personal computer: Windows.
Gateway to the Internet: Google.
Gateway to your social world: Facebook.
What we are talking about is a business that provides a single resort to meet (most of) your needs in a particular arena. I would define a gateway business as one that encompasses a platform that can host applications to fulfill ones needs in that world.
How to develop a successful gateway business? Develop the world inside the gates. Visualize four gates in front of you. You get a chance to peep through each one of these gates to see what’s on the other side. Which gate will you go through? The gate across which you will find the most of what you are looking for. In a gateway business, sometimes you don’t have to be the best, but have to provide an ecosystem that delivers the customers best of what they are looking for, or in other words, you need to be the best platform out there. For example, you can debate that Windows is not the best operating system out there, but it is the one which supports the most applications providing majority of people what they want from their personal computer, making it the best platform for personal computers in the market.
Interesting thing to note here is none of these platforms we consider to be iconic gateway businesses were the first in the field. Windows was not the first operating system, Google was not the first search engine and Facebook was not the first social networking site. They all had someone before them that were not able to develop a formidable platform. This brings up two important points. First, a gateway business, though considered to be less vulnerable have its own vulnerabilities and is not indispensable. If you have a gateway business, better remain on your toes and keep evolving. Second, if you are planning to start a gateway business, and you think you can do better than what’s out there, go for it. Just something else already dominating the market is not a barrier enough to abandon the plans.