I far as I can tell the discussion on REST web services gained momentum back in 2002 (
Roots of the REST/SOAP Debate) when it became apparent that there was nothing "simple" about SOAP. SOAP-based web services quickly became more and more complex to accommodate all sorts of features that benefited only a small percentage of applications but imposed the resulting complexity on everybody - so everybody has to put up with complexity they don't derive any value from (EJBs anyone?).
In 2004 the statement was made that
80% of the developers used the XML over HTTP version and 20% used the SOAP version
(
Complexity of REST and SOAP) for Amazon web services - indicating that there was a real interest in web services that were "lighter-weight" than SOAP. At the same time there were statements that REST web services were less taxing on the hardware infrastructure compared to SOAP web services.
As time goes by the number of SOAP related extensions is still growing while the need for light weight web services hasn't subsided.
[ June 13, 2007: Message edited by: Peer Reynders ]