Consider this scenario:
Stakeholder(s): Let's build a web application to manage user's financial data.
Scrum team: Ok, let's do it. . . .
After 3 sprints
Stakeholder(s): Let's also implement a mailing system, so that when user's financial status is not good, (s)he would be warned.
Scrum team: Ok, it's not that hard. We'll do it. . . .
After 5 sprints
Stakholder(s): Let's become a mailing provider.
Here, how should scrum team guide stakeholder to stay inside the scope of scrum vision? Maybe a more fundamental question is, should the at all?
Update: Of course there is a product owner. But by scrum team I meant PO, SM, and Team.