Normally, when you talk about enterprise-level software approaches, you are not talking about open source in any form of the term. The OpenSocial foundation is working to change this approach by looking into providing a specification that is well defined enough to serve internal business models and still provide security.
In many workplaces, proprietary software governs our email, company profiles, and even our interaction with other members of the organization through messaging systems. There is no reason why a company profile cannot be driven by an OpenSocial container; why the tools you use to create expense reports, add vacation time, or even deliver presentations cannot be OpenSocial applications; or why messaging systems cannot be built using activity streams and messaging systems defined through OpenSocial. This area of development has exciting implications for application developers, presenting them with the opportunity to build productivity tools for businesses in the same way they build applications on open social networks.