Object Oriented Programming Oversold!. Статья чрезвычайно полезная - автор говорит про общеизвестные, но явно игнорируемые адептами ООП моменты. К сожалению, в нынешнем объектно-ориентированном шабаше вряд ли его голос будет услышан.

"...People read this section and keep mentioning "wonderful" products that allow automated mapping of relational tables to OOP objects. However, these appear not to be an improvement over traditional or table-oriented paradigms, but simply a tool to close the gap a bit. Often times one has to "dumb down" their interaction with relational databases in order to get a workable match. Users of such tools often call the database a "persistence mechanism" (storage system). This is an insult to the full power of relational theory. It is almost like defining a car as "a place to store gasoline...".