Over the past year-ish IANA has allocated the last few ipv4 /8 ranges. Everything between and including 1/8 and 223/8 has been allocated, leaving only multicast and "future use" unallocated at the top of the range.
At the current rate of usage it will be a while - possibly three or four years - before these have been used up. We are then looking at ipv6, which is going to be a nightmare to block: for one thing there will be 65000 times as many IP ranges to check and maybe block.
Just thought I'd mention it. The new allocations came to my notice today with a brand new server farm to block. :(
Think I'll retire soon. :)