Simple question: Please show me a case where inheritance and/or full data encapsulation makes sense for business/domain objects on the implementation level. 

I'll steal the low-hanging fruit: Address. Address is a great candidate when you look at an OOA model as you could model yourself to death having BaseAddress(BA) and BA<-StreetAddress(SA) and BA<-PostalAddress(PA) and SA<-US_StreetAddress and SA<-DE_StreetAddress and SA<-UK_StreetAddress and so forth.

When it comes to implementation, you'll end up refactoring the class into on thing: Address. There's probably an AddressType attribute and there's a Country field that indicates the formatting and since implementing a full address validation component is way too much work that feature gets cut anyway and hence we end up with a multiline text field with the properly formatted address and stuff like Street and PostOfficeBox (eventually normalized to AddressField), City, PostalCode, Country and Region is kept separate really just to make searching easier and faster. The stuff that goes onto the letter envelope is really only the preformatted address text.

Maybe I am too much of a data (read: XML, Messages, SQL) guy by now, but I just lost faith that objects are any good on the "business logic" abstraction level. The whole inheritance story is usually refactored away for very pragmatic reasons and the encapsulation story isn't all that useful either. You simply can't pragmatically regard data validation of data on a property get/set level as a useful general design pattern, because a type like Address is one type with interdependency between its elements and not simply a container for types. The rules for Region depend on Country and the rules for AddressField (or Street/PostOfficeBox) depend on AddressType. Since the object can't know your intent of what data you want to supply to it on a property get/set level, it can't do meaningful validation on that level. Hence, you end up calling something like address.Validate() and from there it's really a small step to separate out code and data into a message and a service that deals with it and call Validate(address). And that sort of service is the best way to support polymorphism over a scoped set of "classes" because it can potentially support "any" address schema and can yet concentrate and share all the validation logic (which is largely the same across whatever format you might choose) in a single place and not spread it across an array of specialized classes that's much, much harder to maintain.

What you end up with are elements and attributes (infoset) for the data that flows across, services that deal with the data that flows, and rows and columns that efficiently store data and let you retrieve it flexibly and quickly. Objects lost (except on the abstract and conceptional analysis level where they are useful to understand a problem space) their place in that picture for me.

While objects are fantastic for frameworks, I've absolutely unlearned why I would ever want them on the business logic level in practice. Reeducate me.