In Beyond the RDBMS Sean references Martin's post which in turn points us to a paper (gotta love the web in action) promoting "The End of an Architectural Era". This paper advocates the complete rewrite (well trashing actually) of current RDBMS code in favor of specialized "engines".
It's an interesting read with some good points until I got to this:
Our current favorite example of this approach is Ruby-on-Rails. This system is the little language, Ruby, extended with integrated support for database access and manipulation through the “model-view-controller” programming pattern. Ruby-on-Rails compiles into standard JDBC, but hides all the complexity of that interface.
Rails compiles to JDBC? Now I'm questioning the the whole paper...