What's the distinction between SOA and web services? Are web services simply one direction that SOA can take?
Again, the web site analogy applies here. For instance, you might ask, "Well, what's the distinction between HTTP and Amazon?" Web services are simply the protocol layer, important because they're a key element of interoperability, but they are only a path to the value a service offers.
You shouldn't have to obsess over the content of the SOAP header any more than you should obsess over the content of the TCP/IP header. Web services is basically the plumbing, and SOA is the functionality your services collaboratively deliver.
Why shouldn't developers believe that all this talk about SOA is just hype?
SOA is simply the promise of carrying over the collaboration enabled by web applications to the collaboration of business functions. It will happen because global computing will affect enterprise integration just like it affected client-server computing. While the details may vary from what we see now, nothing can stop this next wave of global computing.