Journal of Product Innovation Management has an interesting article on Spurring Cross-Functional Integration for Higher New Product Performance: A Group Effectiveness Perspective.  The article recognizes, that cross functional integration is crucial, but difficult to do:

Firms are increasingly assembling cross-functional new product development (NPD) teams for this purpose. However, integration of team members’ divergent orientations and expertise is notoriously difficult to achieve. Individuals from distinct functions such as design, marketing, manufacturing, and research and development (R&D) are often assigned to NPD teams but have contrasting backgrounds, priorities, and thought worlds. If not well managed, this diversity can yield unproductive conflict and chaos rather than successful new products.

The paper lays of the result of a formal study based on group theory that scientifically validates that cross-functional integration does have a positive effect on R&D effectiveness:

The model developed from this theory was then tested by conducting a survey of dual informants in 206 NPD teams in an array of U.S. high-technology companies. In answer to the first research question, the findings show that cross-functional integration indeed contributes to new product performance as long conjectured. This finding is important in that it highlights that bringing together the skills, efforts, and knowledge of differing functions in an NPD team has a clear and coveted payoff: high-performing new products. 

The study finds that two types of factors impact cross-functional integration:

Specifically, social cohesion and superordinate identity as internal team factors and market-oriented reward system, planning process formalization, and managerial encouragement to take risks as external team factors foster integration.

Authors recommend that BOTH factors need to be addressed effectively to integrate teams:

These findings underscore that spurring integration requires addressing the conditions inside as well as outside NPD teams. These specialized work groups operate as organizations within organizations; recognition of this in situ arrangement is the first step toward better managing and ensuring rewards from team integration.

Clearly, internal factors are much more difficult to address in diverse teams that are dispersed across multiple locations.  In fact, it is very difficult to get virtual teams to believe that they are a single organization.  That is where R&D managers can help!