I'll spend some time elaborating on the content tomorrow, but up front, I'd like to state my reasons for participating in this effort. I'm not exactly known to be a web services fan, so I had numerous people ask me why I'd take part in something like this. To my view, this is not at all a conflict — I see SOA as a high-level approach than can be realized with multiple sets of technologies. While I believe that RESTful HTTP is actually the best option out there, I concede that people might think differently about this. But there are some high-level goals that are independent of the architectural style and being used.
So I believe that SOA is a good idea, I also believe that web services based on SOAP/WSDL/WS-* suck, and I believe that REST is a perfect match for SOA. Of course this statement would be entirely meaningless if you defined SOA as the architecture of web services. I don't.
The reason for the manifesto being somewhat vague, in my opinion, is a good one – describe the values that are common to those who aim to improve upon the typical company's IT landscape, regardless of the actual technical architecture.