If you don’t have good architects, big systems will end up as big balls of mud. A lot of companies live with it, but there are certainly big payoffs if you can avoid it. The main problem is that there aren’t enough good architects to go around. One of the advantage of a RDBMS is that it is fairly easy to understand so below average programmers can still get systems running. Below average programmers will not build the best architectures, though. So, the fact that RDBMs lead to big balls of mud is actually a sign of an advantage. You can use a RDBMS when you have good architects and when you don’t. You’ll end up with completely different systems, but that is because of the quality of your architects, not because of the technology you use.
He discusses RDBMS mostly in relationship with OODBMS and things like Prevaylor. I am looking forward to seeing more on this from Ralph, as it in many ways ties in to my own thoughts on use of databases.