XML becomes pervasive on the web. I think it's great that a lot of web APIs support both REST and SOAP, there are some situations where I use REST and some where I use SOAP, and being able to use both is great.
This is like Amazon's S3 interface, they have both REST and SOAP APIs. It looks like more people use the REST API, and I use it myself, mostly, but I'm building a new tool for protein structure exploration that will use both, and I'm glad I have the choice.
It's all about the freedom to choose.
