In the 14 years I've been working in this industry, the approach of creating flat designs to demonstrate something interactive has always sat uncomfortably with me.
This creates issues by its very nature - be that, helping fuel the notion of passing the buck from one team on to the next, or just purely missing something, because of all the possible outcomes weren't considered during scoping (which in itself is a topic for a blog post!). Clients never really knew what they were signing off, and we were always (somewhat naively) surprised when they had design amends during development because something didn't behave quite as they were expecting.
The relatively new - but still far from widely adopted - approach for creating interactive designs, where we can easily get users to test how something is expected to look and work is, for me, a revolutionary thing for digital design - whether it be for product or marketing purposes. Tools such as InVision, allow designers the freedom to explore how the product will work and, I believe, take more responsibility for the end product. It allows you to test and learn and iterate easily, meaning the product will ultimately benefit, as will your end users.
At Owl & Giraffe, we believe in iterative design and user research to get the best out of the projects and products that we work on. In our most recent project with Heineken, we developed a fully functioning prototype for their online trade mobile website. This was tested at each stage of design with users in a format which made sense to them. The website was in their hands, on their mobile and it 'worked'. This gave us invaluable insight into how they expected things to function and allowed us to easily iterate and improve the product that we were developing.
Photograph by João Silas — https://unsplash.com/photos/o3FYxekXOBc