This rant by major database guys against mapreduce is pretty telling.
The thing that disrupts you is always uglier and worse in some way. Less features, less developed. But if there's a 10X price win in there somewhere, the cheap rickety thing wins in the end.
Think Linux vs. AT&T Unix, or mysql vs. Oracle.
I'll also take exception to the claim that schemas won out over unstructured data in the 60's. Unix ultimately trounced Multics and its ilk, not simply because of quasi-open source and economics, but also because the programming model was superior. "A file is just a stream of bytes" was a radical departure from the record and key oriented approaches that were dominant at the time. Some folks haven't stopped fighting the war though. Oracle's multi-decade messaging effort deserves more credit for the acceptance of databases as industry-standard tech than the idea that warring academics came to realize some deep truth about the way data "should" be stored.
Linear perf, linear cost scale, and the programming flexiblity of unstructured Unix-like I/O in GFS or fluid schemas in Bigtable. All good.
And I wouldn't be surprised if the adoption curve, even for conservative Fortune-500 companies, was quicker than we've seen in the past. Bolt a map/reduce cluster onto the side of your data warehouse and mine those CRM records for business insights. Sounds like a startup idea we'll be seeing soon enough. ;-)