The problem
A responsibility matrix is simpler than a full RACI — it's a direct mapping of tasks to owners, often with due dates and status. It's the tool you reach for when RACI is too formal but you still need explicit accountability. Project kickoffs, workshop action plans, team reorganizations — any time you have a list of deliverables and need to know who's doing which one.
The whiteboard version builds naturally: list the tasks, name the owner, write the date, track status (Not started / In progress / Done). Simple. Clear. The problem is that everyone in the room sees the whole matrix, but nobody leaves with a copy that matches the board exactly. The PM takes a photo and promises to 'clean it up and send it around.' That cleaned-up version takes an hour to produce and is often slightly wrong.
Meetings that end with an action list on a whiteboard but no digital artifact repeat themselves. The next meeting starts with 'where are we on the items from last time?' because nobody can find the agreed list. The responsibility matrix is the answer — if it gets captured properly.