While I partially agree with you, to me the ease of making summaries of data across different sets, makes SQL a better choice for where higher order calculation

While I partially agree with you, to me the ease of making summaries of data across different sets, makes SQL a better choice for where higher order calculations are required. Writing a distributed map reduce query in erlang is both harder to make fast, and harder to understand. For something like static html pages, for say a source control web app like Github, Riak or some other document store is a great choice. But for something like a invoicing/accounting app like FreshBooks, where you need to summary and filter across multiple accounts, invoices, staff, etc., then SQL is much easier to build a OO backed system. (Although there would still be events in there as well, like notification systems, etc.)