Chris Brogan sum this up nicely by saying "paper doesn't have a new browser window." In other words, doing something on paper creates a good obstacle to distracting yourself with Facebook, email, or some other non-essential task.
Chris made his comment in the context of planning and task management. I apply that comment to the process of brainstorming and or reflecting. Taking the time to read a book, to write some ideas on paper, or to simply go for a walk give out brains time to wonder and develop new-to-us ideas without the distraction of digital input.
Don't get me wrong, I love some of the digital brainstorming and project management tools that we have available to us. There is a time for using those (iBrainstorm is one of my favorite brainstorming apps), but there is also a time for not using digital tools too. As our students grow up in a hyper-connected world, it is will be increasingly important to take the time to teach them when being connected might not be the best choice.