Number #1 rule for all information systems is to always backup your data. A lot of users experiment with Easy!Appointments source code trying to add new custom functionality, add new fields in the database and tweak the main workflow. The best way to secure data is to keep frequent backups, something that should be reasonably easy depending the hosting provider tools.
Furthermore, once the database records start to grow in number and there is valuable customer information stored within the app and webmasters need to make sure that they maintain copies of these data. In the future Easy!Appointments is going to provide API methods that will enable users to access those information from other software systems, so data integrity is very important.