The business case above shows that with adoption level of just 40-50% and with price points of just $60 / month /employee which includes a mobile handset, phone, software, voice and data plan the size of the market is substantially large at $50B-$70B annually.

Small and Medium size enterprises don’t have the luxury of a dedicated PBX system- IP or otherwise. Telecom operators such as AT&T and Verizon can offer a hosted unified communications solution which entails mobile and fixed-line convergence, instant messaging, presence, video and teleconferencing over PC and mobile phones and integration with mail exchange and messaging systems and offers a unique proposition to small and medium-size enterprises.
SME data as defined as companies up to 500 employees form a large part of US economy as indicated by 2007 data published by US census bureau. Many / most of them can’t afford a dedicated PBX system. Unified communications provides them not just fixed mobile convergence value but also a host of other features; access to which currently requires them to spend a significant amount– conferencing, instant messaging, presence etc.

Hosted unified communications offering to SME is indeed the answer to eroding telco ARPUs.