Interesting comparison of active http server usage within netblocks
(based upon ~6 million addresses polled - 06/03/2007)

The leftmost number is the leftmost dotted decimal segment of a
version 4 internet address block. There are 256 of these in the entire
internet IPv4 address space.

Notes:

Some gaps may be the result of reserved blocks. A percentage of ".1%"
means "equal-to or less-than .1%."

The 208 netblock was used for initial testing, and so may be slightly
overstated. However; any block with 3% or more should be considered
to be a very active block. Others should fill in as more data is collected.

Other reserved ranges:
92-95, 100-115, 173-187, 197, 223

Other U.S. DOD:
214, 215

A block designated as being under a particular authority,
(e.g. "Asian authority, APNIC") does not (necessarily)
mean that it as been allocated.