Oil catch cans are a hotly debated topic, yet one fact is still irrefutable; oil blow-by will always be a real byproduct of the modern direct-injection engine. Intakes, charge pipes, and turbos all come into contact with the stuff over time. Sometimes, even newer, low mileage vehicles develop blow-by issues. With direct injection, fuel is injected directly into the cylinders, eventually resulting in carbon buildup on the valves. This was not an issue with port injection, since fuel injectors were placed in the intake manifold. The air-fuel mixture is sprayed directly on the valves, essentially cleaning them each time an injector fired.
Carbon and oil buildup in direct-injection engines can negatively impact vital engine components and can result in an expensive fix later down the road. I can go into long, excruciatingly deep detail about the dangers of blow-by, but I've given you the basics of what you should know. For more information, I strongly suggest that you take a look