[dagheti]

I think part of the backlash is coming from developers on web-applications that have business models that require scaling to very large loads before they make sense. This puts a premium on keeping things very cheap (no heavy commercial SQLDBMS), and inherently scalable (hierarchical).

Web developers on these types of projects cannot either a: buy a "real" SQLDBMS, or b: charge their customers so their business model makes sense without a huge number of transactions. This means they are willing to suffer it out with solutions that don't provide flexibility or data correctness guarantees of a RDBMS.

This is just a guess, but it's quite likely that it is the rise of hyper-scale-intensive, speed-intensive, revenue-light business models that drives devs towards deciding SQL isn't worth it.

[silentbicycle]

Postgresql is free.

I'm not going to claim it's perfect, but it's pretty damn good, and postgres + intelligently used caching (such as memcached) goes a long way.

[kragen]

Well, you're right that licensing cost can't be the reason, although ten years ago it could have been. But I think the "inherently scalable" item may have something to it.