I mostly agree with the author. But if you're adding such utility / helper functions to the BO (business object), please make them static. Just pass the BO itself to the static method. In my real-time application we have e.g. classes like Point, Line, Path,... which are instantiated very frequently, and there is a huge amount of such instances. If the methods are not static, every class instance would have them in memory. That's not good.