The Internet Assigned Numbers Authority (IANA) assigns IPv4 addresses to the regional Internet registry (RIR) in blocks that are equal to 1/256th of the entire IPv4 address space. Each block is referred to as a "/8" aka "slash-8" and includes just over 16 million IP addresses. The most recent assignment means that there are now only 7 of these blocks available.
The last two will be assigned according to demand, and after they're gone, each of the remaining five "/8" blocks goes to one of the five RIRs. This decline has happened even faster then expected. In mid-October, IANA and ARIN expected the supply of IPv4 addresses at the IANA/RIR level to last until early 2011.
Now, as Owen DeLong an IPv6 Evangelist for Hurricane Electric, told me "These [last] two [/8 blocks] will likely be issued to APNIC [The Asia-Pacific RIR] some time this month or very early in January. At that point, there will be no more global IPv4 free space and we will begin the countdown to RIR exhaustion."
As Takashi Arano, CEO of the Japanese Internet company Intec NetCore (Japanese language site) notes on his IPv4 Address Report wrote, "The prospect of the forthcoming hiatus in the supply of IPv4 addresses also appears to have hastened some network deployment plans on the part of many service providers, and while the RIRs continue to adhere to the policies and practices of allocation of addresses in response to demonstrated need, there is a noted escalation of demand for addresses in recent times that is likely to persist in the coming months."
This means his automated estimate of when we're going to run out of freely available IPv4 addresses may have been too conservative. Arano added, "The continued escalation of demand levels is also adding some pressure to the demand model."
You can say that again. For most people, you still don't have anything to worry about. But, if you're a network administrator, this just underlines, once more, that it's time to get cracking on your IPv6 plans.