Security and liabilities are a concern of mine as well. As far having everything on one network grid, my understanding is that Google is releasing the core as open source so your company can set up its own wave service. This can be kept for internal use only or bridged to a similar set up at another company. Part of the looong demo simulated this, showing the platform agnostic capability.

There are still a lot of issues that need to be resolved and plugins that need to be developed. A really good VOIP plugin for example.