Re: "We have now run out of IPv4 addresses"
THIS! THIS! AND (MOSTLY) ONLY THIS!
Think about it this way - had they only added 1 additional address byte, we could have had 253 additional Internets. But that would suck implementing in hardware, which likes even byte boundaries. Two additional bytes would have take it up to 65,000-ish Internets, but still not optimal for hardware. 4 bytes would basically have made an Internet of Internets, and would land them squarely into 64-bit integers - nice and even and easy to do in hardware. And still relatively memorable, without needing any colon-cleansing place holders.