I just saw this blog post in rebuttal to Martin Fowler's DatabaseThaw article. It's a typically well-thought out response from Typical Programmer. The short summary is that he rejects Fowler's criticism of using RDB's as the mechanism for application integration. (And don't dismiss him as simply a RDB bigot - he's not shy about nailing relational gurus, as in Relational Database Experts Jump The MapReduce Shark).
TP's arguments ring true to me, although in my experience it takes a very concientious DB shop to fully maintain the "encapsulation of data and operations" across many applications, many custodians, and many developers.
It would be great if Fowler's vision of the integration point being HTTP rather than SQL solved all our problems. Loose coupling is a wonderful thing to have. But so far I'm not seeing how this provides equivalent performance for all cases, and how it avoids the problem of data model mismatch.