You, as a developer, need to control the quality of the data entered in to your application. This applies not only to applications distributed to far-flung places, but to applications you will use yourself.
As I write this lesson, I’m working with a large medical provider who, at this point, can’t report its research findings to its granting agency. The reason is that the designer of the database where the research was supposed to be compiled failed to institute good data validation procedures. The resulting chaos caused by questionable data is costing this provider a lot of money (my fees) plus is putting its grant in jeopardy. Ignore this part of database design only at your extreme peril.