2. There is no easy way to determine where a VOIP call came from. You know that old TV/Movie gimmick about tracing a phone call? Well it doesn't exist, not with POTS, anyway. As soon as you make a POTS phone call, you know exactly where it came from. VOIP ruined all that.
3. VOIP phones require connectivity in places where you do not necessarily want to have connectivity, such as data centers, which frequently not only don't allow VOIP phones, but won't even allow you to bring in a cell phone.
4. Spoofers are already using VOIP to spoof phone numbers. It is in fact, point #2 I listed above that makes spoofed calls possible where as they aren't doable with POTS. But you have a plan to block spoofing if everyone goes to VOIP. This essentially means you're going to enable filtering of traffic in ways that are going to spill over into non-VOIP traffic that you do not want to happen or we end up with China Firewall 2.0.
