Mobile computing is exploding. Gartner expects tablet sales to overtake computer sales by 2017 and that doesn't include the fact that world wide mobile phone sales are almost an order of magnitude higher than computer sales are today. For us that means ensuring that everything we deliver is easily consumed through a mobile device.
The percentage of web pages viewed on a mobile device grows every day. Modern websites can be designed to adapt to the size of the screen on which they are displayed. It's referred to as "Responsive Design" and it's something we think about with every new project.
Responsive design also lets us deploy mobile applications from a web server rather than a native applications. Web based mobile apps have a number of advantages. They don't need to be downloaded and installed on a device so they are available almost instantly. The same version runs on an iPhone, Android, or Windows Phone. You can easily runs A/B tests where some users get a new experience and another set acts as a control group.
Of course there are some things that are best done natively on a device. Anything that whose performance is heavily dependent on hardware like a game or an app that runs without a network connection are good examples. There are also business considerations for native app development. It may be that your users would happily pay for an App but be hesitant to sign up for a web app that charges money.