[mks]

OOP is great when your main focus are data structures. Many enterprise applications are basically just transforming data from one system to another. Being able to come to an unknown code and figure out what is the format of input and output just by reading couple of classes is a godsend. Even in this case use OOP features sparingly (beware of deep hierarchies, contrived polymorphism etc).

On the other hand when your problem is more about algorithms and evaluation of data you might choose more functional approach.

Hybrid (object+functional) approach is getting even to the enterprise world - SOA suggests to have dumb (possibly immutable) data objects for business objects (just like struct in C) and service objects that perform operations on these data objects (not unlike functional programming). Similar pattern is with dependency injection frameworks that rely heavily on singletons (Spring) - many beans become just containers for stateless functions.

OOP is not silver bullet (nothing is for that matter), but it is a very useful tool.