Most of those I spoke to at WS-REST felt was that media types, tools, and frameworks for REST have been growing slowly and steadily since 2008, but lately there's been a major uptick in activity: HTML5 is giving browsers and web applications a makeover, OAuth is an RFC, several Atom extensions have grown, Facebook has adopted RDFa, Jersey is looking at Hypermedia support, etc.
But, coming out of the WS-* vs. REST debates, it is interesting in noting what hasn't happened the past two years, since the W3C Workshop on the Web of Services, which was a call to bridge-building. As expected, SOAP web services haven't really grown on the public-facing Internet. And, also as expected, RESTful services have proliferated on the Internet, though with varying degrees of quality. What hasn't happened is any real investment in REST on the part of traditional middleware vendors in their servers and toolsets. Enterprises continue to mostly build and consume WSDL-based services, with REST being the exception. There has been, at best, "checkbox" level features for REST in toolkits ("Oh, ok, we'll enable PUT and DELETE methods"). Most enterprise developers still, wrongly, view REST as "a way of doing CRUD operations over HTTP". The desire to apply REST to traditional integration and enterprise use- cases has remained somewhat elusive and limited in scope.
Why was this?
Some might say that REST is a fraud and can't be applied to enterprise integration use cases. I've seen the counter-evidence, and obviously disagree with that assessment, though I think that REST-in-practice (tools, documentation, frameworks) could be improved on quite a lot for the mindset and skills of enterprise developers & architects. In particular, the data integration side of the Web seems confused, with the common practice being "make it really easy to perform the required neurosurgery" with JSON. I still hold out hope for reducing the total amount of point-to-point data mapping & transformation through SemWeb technologies like OWL or SKOS.
Perhaps it was the bad taste left from SOA, or a consequence of the recession. Independently of the REST vs. WS debate, SOA was oversold and under-performed in the market place. Money was made, certainly, but no where near as much as BEA, IBM, TIBCO, or Oracle wanted, and certainly not enough for most Web Services-era middleware startups to thrive independently. It's kind of hard to spend money chasing a "new technology" after spending so much money on the SOAP stack (and seeing many of the advanced specs remain largely unimplemented and/or unused, similar to CORBA services in the 90's).
Or, maybe it was just the consequence of the REST community being a bunch of disjointed mailing list gadflys, standards committee wonks, and bloggers, who all decided to get back to "building stuff" after the AtomPub release, and haven't really had the time or inclination to build a "stack", as vendors are prone to.
Regardless the reason, the recent uptick in activity hasn't come from the enterprise or the enterprise software vendors offering a new stack. The nascent industries that have invested in REST are social computing, exemplified by Twitter, Facebook, etc. and cloud computing, with vCloud, OCCI and the Amazon S3 or EC2 APIs leading the way.
We're going to be living with the results of this first generation of HTTP Data APIs for quite some time. It's time to apply our lessons learned into a new generation of tools and libraries.