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 sprintsStakeholder(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 sprintsStakholder(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. 
How to guide stakeholder(s) not to get far from the scrum vision?
agile;scrum
The very purpose of Agile methodology and sprint development is to support the new and changing requirements of the stakeholders.  If this project were being managed in a waterfall way these kinds of request would threaten the success of the project.If there is one thing that I learned, You can't fight scope creep.  It is like swimming against the current of a river, you can fight and kick and scream all you want but in the end the river will sweep you away.  The bottom line is that the stakeholders want is what should be delivered or the stakeholders will be unsatisfied.A further advantage of your situation is that they are not changing established requirements, just expanding the scope to include additional features.  This is fine as long as the deadline moves forward with scope creep.  This only becomes threatening to a project when a firm deadline is set.