From Forbes:
The Internet is supposed to be limitless–a boundary-free exchange of digital information and profit. So how can it be running out of real estate?
The answer, according to information technology experts, lies in cyberspace’s ever-growing popularity. In theory, each new user who wants to log on needs a new address, as does each new Internet-enabled gadget, like smartphones that can access the Web. Routers, which allow multiple users and devices to use a single address, are helping stave off the problem for now, but it’s only a stopgap measure.
Currently, the Internet has room for 4.3 billion addresses. About one-third of those are already in use, and more than another one-third are spoken for. By 2012, there will be some 17 billion devices connected to the network, estimates research firm IDC.
But an update to the rules that govern how data moves along the Internet could solve the real estate crunch before it starts.