Mark has such a deep dedication to his work he once walked two miles in twenty inches of snow to open his office to customers (in a southern state with only a few snow plows).
When someone (or something) is devoted to a task to a point where it becomes obsessive or completely unreasonable. If someone is "dedicated", they will stop at absolutely nothing to achieve their goal, no matter what the outcome and even at the expense of others. It could also mean when someone is trying far too hard at something.
