A Web Service is a software component that is described via WSDL and is capable of being accessed via standard network protocols such as but not limited to SOAP over HTTP.
A web service is a software component that does one very specific thing, such as retrieve a customers account number, and is used in combination with other web services to perform certain functions. Web services can be reused, thus are very handy.
Clearly Steve Rubel is talking about something entirely different:
The leading players on the web all see the train coming. They are wisely creating APIs and turning themselves into plug-and-play services, not just big destinations. YouTube is just the latest to do so today. Amazon has S3. Google has OpenSocial and an extensive library of APIs. As does Microsoft. Facebook is allowing its applications to live outside the site. Twitter is an API first and (eventually) a business model second. Finally, the booming widget economy shows the promise of small content that can go anywhere.
These are the leaders. But everyone - including marketers - will need to think of their online brands not as sites but as portable services that can go anywhere and everywhere the consumer wants. Without such appendages, no brand will ever be able to break through the online clutter such unlimited choice offers.
In this context the term web services is clear enough. We just need to be careful when we do presentations of what is meant by a term. The context is not always as clear as we assume.