SOAP is fragile, bloated and slow. It goes against what the very essence of a service should be, i.e. to expose functionality in as accessible and inter-operable way as possible. The higher up the WS-* stack you go, the less supported it becomes - eventually only the Big Enterprise frameworks from MS and IBM support the complete WS-* stack.

WSDLs promote code-gen and as different SOAP frameworks have varying levels of WSDL support, you often end up with broken + ugly code-gen when trying to consume from different SOAP stacks. SOAP is also a brittle format where even a small namespace change can break the entire request, this makes versioning (a core part of evolving services) extremely difficult.

I generally prefer clean HTTP APIs with Cool URI's and JSON which is a much faster, smaller, more versionable and tolerant format that provides a better programmatic fit than SOAP/XML: http://www.infoq.com/presentations/Heretical-Open-Source