I'm involved, as a software developer, in an early stage (pre-profit) start up. The product is at a point where the basic core is implemented and we are building out features and adding polish, so the fundamental idea of the product is solid. However, the sales and business development folks like to derail development by asking for development of quick prototypes, new features, or demos to support potential sales mid-sprint. This constant interruption derails development and causes features to take longer, because of the time it takes to re-read the code and remember where you were.
In an early stage start-up, is it appropriate for development to ask that any new features wait until the start of the next (2 week) sprint? Or is it more important to actively chase prospects with demos and prototypes? Perhaps kanban is more appropriate, so that developers can finish the task they are working on properly, but allows the injection of high priority tasks without have to wait until the end of a sprint?
The phrase "failure to plan on your part does not constitute an emergency on my part" comes to mind, but I don't know if that attitude is appropriate in a start-up, where it is important and necessary to rapidly respond to change.