In spite of the importance of service value networks (SVNs) in today's service sectors, academic studies of SVNs, in terms of their formalisms, models and value creation processes, are still lacking, with only sporadic publications available. This paper intends to make a contribution to the formal studies of SVNs with a threefold aim: (1) to provide an overview of existing work on value creation processes in SVNs and SVN models, (2) through this exposition, to propose a formalism for measuring service utility for SVNs, and (3) to illustrate this formalism through a real world SVN scenario based on China's mobile services market. The proposed formalism consists of a formal definition of service utilities for both primitive and complex services and a systematic approach with repeatable processes for measuring these utilities. Among several potential practical uses, this formalism can be embedded into a software system as a decision tool for service selection, composition and pricing. In addition, it can also serve as a business services analysis tool during the early stages of developing software intensive service systems, where business service abstractions can be represented as SVNs.