Well, IMHO, what is easy for the developer isnt always the perfect way, right? If your web services have different functionalities and are distinct entities, it makes sense to separate them. Anyway the WSDL has to go over the net and the "small-is-beautiful" principle applies..
Also there is the issue of version control. Publishing multiple services in the same WSDL inexorably links them to one another - something you want to avoid. As you evolve your services you may have to publish multiple versions of the interface to the same service for backward compatibility and each client installation may require a different version mix of the different endpoints, potentially leading to a combinatorial explosion of customized WSDLs. Bottom-line - stick with the smallest WSDLs possible - but no smaller.
You can usually manage common portions between WSDLs with XSD and WSDL imports. But again make sure to include a version identifier in your import filenames. WSDL file imports [ July 12, 2006: Message edited by: Peer Reynders ]