Commodity hardware + open source = asterisk PBX
This in and of itself is not a game-changer. This is the equivalent of the "garage hosting" model of ISPs that was prevalent through the early 90s, with Mr. Modem Bank selling to local customers. However, it presages what larger players can do with the same technological building blocks -- after all, those little ISPs led to AOL and Earthlink.
"Asterisk is a complete PBX in software. It runs on Linux and provides all of the features you would expect from a PBX and more. Asterisk does voice over IP in three protocols, and can interoperate with almost all standards-based telephony equipment using relatively inexpensive hardware.
Asterisk provides Voicemail services with Directory, Call Conferencing, Interactive Voice Response, Call Queuing. It has support for three-way calling, caller ID services, ADSI, SIP and H.323 (as both client and gateway). Check the Features section for a more complete list.
Asterisk needs no additional hardware for Voice over IP. For interconnection with digital and analog telephony equipment, Asterisk supports a number of hardware devices, most notably all of the hardware manufactured by Asterisk's sponsors, Digium. "