this has probably already been thought-out, but outbound reachability testing *from* the address block to a representative spread of addressing makes much more sense and would be much more indicative of forwarding (versus routing) problems, and would do so with some method and statistical reliability. presumably that is coming and just hasn't been discussed or carried out yet. It's a good idea, but of course that requires someone in the allocated block to have a list of addresses to ping, all over the net.
as i said privately to someone, a few problems o the scale of destinations is far to large. o how are you to know what is an important host inside of a complex enterprise? the granularity of routing/filtering within sites is not externally visible. o many of a large complex enterprise's sources from which it may be desirable to test may be in 1918 space. o the pingees may not like being pinged. the goal here was for isps and enterprises who want to be good citizens to be able to test. randy