Adam Trachtenberg at ONLamp.com:
"Therefore, REST advocates claim, there's no need to layer the increasingly complicated SOAP specification on top of these fundamental tools. [...]
There may be some community support for this philosophy. While SOAP gets all the press, there are signs REST is the Web service that people actually use. Since Amazon.com has both SOAP and REST APIs, they're a great way to measure usage trends. Sure enough, at OSCon, Jeff Barr, Amazon.com's Web Services Evangelist, revealed that Amazon handles more REST than SOAP requests. I forgot the exact percentage, but Tim O'Reilly blogged this number as 85%! The number I do remember from Jeff's talk, however, is 6, as in "querying Amazon using REST is 6 times faster than with SOAP"."