The problem about RDBMS in web world is that it just don't fit the scenario. When RDBMS was born, it deal with large, relational, but relatively static data. You can use whatever query to get the organized result. But today's web world is very different. We have relatively static queries (get top 10 stories, get account XXX most recent posts etc.), but the data are changing all the time. Consistent query may be a good start to solve the problem.