I recently read an article, written by Ken Deutsch, titled, "Is the Internet Doomed?"
It spoke about the vast number of IP addresses being comsumed at an alarming rate.

Quote:

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I'm not talking about the domain names followed by dot-com or dot-net (URLs). We can have almost an infinite number ot those by adding wharever letters we want after the dots. I'm talking about he Internet Protocol (IP) numerical addresses underneath those that refer to the specific devices that are hooked up. Each cell phone has one, each computer has one and even microwaves now have them.
The Sunday Times of London quotes several big-time scientists as saying that within three years this shortage of IP addresses will begin to cripple our use of the net. The Internet will slow down to a crawl, Then it won't work.

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The article states that while the prospect is scary, there is a solution. But it also states that the different versions aren't compatible.
Do I hear the cash register's ringing up new sales for items like those mentioned above? Probably.

IPv6: The Next Generation Internet!

There's even a count-down clock for this event:

IPv4 Countdown

This issue has been getting closer to melt down. It used to be that ISPs could get by with a fraction of the IPs compared to subscribers. This was because, with dialup, only a small percentage of subscribers were online at any time. But with broadband, most people leave their modem on constantly so it uses an IP. With other IP related devices like cell phones and others. The number IPv4 addresses is dwindling.

Obviously the solution is IPv6 and they have been working on this solution for a long time. But because of compatibility issues its been slow at adoption.