Web Services are becoming the chosen way of exposing interoperable units of work as services. Today consumers and providers of software services talk different languages, and SOAP makes them understand each other.
SOAP can be transported via almost anything, and we sometimes joke that we can even do SOAP over FedEx if necessary. Some architects lay down their design based on SOAP over HTTP services, but as the project grows, they face challenging scalability problems. One of the most accepted ways of addressing these problems is to use JMS. We usually provide HTTP wrappers - still exposing our services as SOAP over HTTP, but those are lightweight fronts that just send or publish a message to a queue or a topic to trigger heavy business logic.
