The first is obvious. If you think saving a few dollars on long-distance is appealing, imagine the draw for companies with whopping phone bills. Using the Internet to make calls not only lowers calling costs, but also equipment costs. Unified messaging can bring phone, email and fax to the same place on a desktop. Click for more .
Businesses pay people to administer their various information networks.
Combining voice and data into one network reduces that burden. Click for more . But technology is the other, and there have been advances. In particular, Session Initiation Protocol. It is both very manageable and designed to be simple for developers to use.