It's funny to me that at the same time people are flocking to languages with strong, flexible type systems (often with compile-time checks), we are fleeing from a strongly typed data interchange format in favor of a dynamic bag of objects and arrays.

I think that's because even if the data interchange format is strongly typed, as a consumer you often still must expect _anything_.

I've yet to work on a project that handles XML where we have a XSD prevalidation step that makes the reading of some deeply nested XML tag feel safe.

Unless we count XML <-> data object binding back in the java days. Not sure that felt any better...

On the flip side, I've only ever not had an XSD when I was building something myself and actively didn't care.

The truth, I tend to suspect, lies somewhere in between. =)

That's not a reason.