In the previous post on the subject I wrote that the RDBMS is dead. I didn't mean that it is dead dead, but rather that it isn't well build to meet some of the newer challenges like linear scalability, high availability etc.
Well, it is one thing hearing it from me - and it is another thing hearing it from someone like Michael Stonebraker.
Michael, was the main architect for the Ingres prototype project at UC Berkely just one year after Codd's paper and (9 years before Oracle was released  and more than a decade before the commercial version of Ingress was released).

Well that was in 1970 - in 2007 Michael recently wrote :
 

In short, the world of 2007 is radically different from the world of the late 1970s. However, none of the major vendors have performed a complete redesign to deal with this changed landscape. As such they should be considered legacy technology, more than a quarter of century in age and "long in the tooth".

Among the new needs Michael cites are intelligence DBMSs (needs a lot of relations), textual and semi-structural data etc. He also said (promoting his own product) that 2007 customers expect high availability, linear scalability.
Michael's main point is that specialization can provide significant performance enhancements vs. the one-size-fits-all approach of RDBMSs. He gives his product (Vertica) as an example for how a column oriented database (vs. the RDBMS row orientation) can outperform RDBMs by a factor of 50. Google's Big table is another example.

Interesting...