A VirtualPrivateNetwork is a private network connecting (some of its) nodes by tunneling traffic over a public network. Alternatively, if you have far too much money, instead of tunneling, you can use a dedicated data circut provided by your TelCo. Most VPNs only tunnel a single connection between two end points that serve to merge two LANs.
Why not? Those things sound kinda useful -- CraigBox
Simple answer: too difficult to code :) more important getting the easy bit going first. Also encryption/compression could very easily overwhelm some people's gateway boxen -- PerryLorier