http://www.nro.net/news/ipv4-free-pool-depleted
All the top level ipv4 address blocks are now allocated. (the first number of your ip address) Doesn't mean that we'll literally run out tomorrow, but, as a 32-bit address space, there aren't enough to go around to give every human an ipv4 address. NAT will keep us going for a while yet I suppose... Of course some blocks are allocated for special purposes, like 127 and 169.