Have you ever experienced how pacified you can feel when a co-worker takes control over your keyboard and mouse? It feels like he or she is intruding into your personal sphere. You might have asked for help, but not to be invaded. It's strange to think of how much "power" the person controlling the mouse and keyboard has. If the person holding the keyboard and mouse isn't aware of the "power" he or she got, and don't bother to include the other person, it's likely the person falls into a apathetic state just watching the screen, and not focusing on how to solve the problem.
When doing a sprint planning you should avoid using a electronic storyboard. My experience is that you end up with one person, probably the scrum master, running the whole show. The other team members will probably sit pacified looking at the screen. Doing nothing, or in best case trying to participate but not being able.
You should rather use a story board hanging on the wall in your office. Perhaps a whiteboard or maybe a board made of gray paper. And Post it’s, of course. This way everyone can participate in the process of adding tasks (and user stories). This promotes cooperation and builds team spirit. Everyone can have hands on experience with the process. It builds understanding for the problem being solved. It lets the team work more in parallel. While one team member is finishing writing one task (or user story), another member can start with the next task (or user story). I'm not saying that an electronic story board can't be used, but you should have very good arguments for using it. It's to pacifying!
If you disagree, remember one of the statements in the agile manifesto; "Individuals and interactions over processes and tools".
What is your experience with electronic story boards?