However it may not be used after 2011. Harry Lewis reports:
If you go to WhatIsMyIp or any of a number of other sites, you can see your own, shown as four numbers, each less than 256, separated by dots. That's about 4 billion possibilities in all, a number that seemed unimaginably extravagant at a time that computers were huge. Today, with computers in everything, even your wristwatch could use its own IP address, and plenty of devices smaller than that. The pool of IP addresses, which were divided into blocks and given out to nations, and within nations to companies and universities and governments, is being rapidly depleted.
According to this report at Enterprise Networking Planet:
The timeline for IPv4 address space exhaustion may not be 2010, but it is likely to be exhausted within the next two or three years at the present rate of IP address allocation. At our current trend rate we've got about 625 days before we will not have new IPv4 addresses available.
The way out is ofcourse IPv6. The next-generation IPv6 system has a 128-bit address space which can support 34 x 10 to the 38th power, or 340 trillion trillion trillion IP addresses.
But the switch may not be smooth, Harry says:
The solution is already known — IPv6, which uses 128-bit addresses. The code is already in the operating systems of computers being shipped today. But the switchover is likely to be hell — think of the switch of broadcast television to digital, with granny suddenly unable to get her soaps. Except that this switch will have a deadline attached to it.