Because I can't help but link to SOAP/REST discussions:
The S stands for Simple
The REST Dialogues
A well reasoned response from the other side: Web Fundamentalism.
My take... there is a reason CORBA, DCOM, RMI, etc. have failed while the "web" has not, and recreating RMI-"principles" atop HTTP (or SMTP or whatever else) may suffer the same fate.
(Update: Sam Ruby has a good post describing some of the imperfections encountered with REST style programming (make sure to follow all of his links; they are all worth reading).)