Scenario Based Testing is categorized under Black Box tests and are most helpful when testing is concentrated on the business logic and functional behaviour of the application .Adopting SBT is effective when testing complex applications.Now every application is complex, then it's the teams call as to implement SBT or not .I would personally suggest using SBT when the functionality to test includes various features and functions.A best example would be while testing banking applications require utmost care while testing, handling various functions in a single scenario would result in effective results.

A sample transaction can be , a customer logging into application ,checking his balance ,transferring amount to another account , paying his bills, checking his balance again and logging out.

In brief ,use Scenario Based Tests when:
1.Testing complex applications.
2.Testing Business Functionality

When designing scenarios ,keep in mind:
1.The Scenario should be close to the real life scenario.
2.Scenarios should be realistic.
3.Scenarios should be traceable to any combination of functionality
4.Scenarios should be supported by sufficient data