@d2d4j - Indeed, just as you say, their own sysadmins will know what is going on with their own network. You and I are in agreement. I don't see any reason to be dropping ICMP responses. One should be able to be confident that malformed packets will not cause any problems, surely? Anyway, I am wandering off topic - my own fault. :-)
Obviously the benefit is to other people trying to work out what is going on.
I did not ask a question was not about whether or not ICMP responses should be generated or not, or whether ICMP should be blocked. Johnson mentioned ICMPs being enabled or otherwise.
I asked about the numbers.
You made me think of something: So here I go off-topic again. Were I designing such a system, then what I could do is just not bother generating an ICMP echo response if I am busy, one thing less to do. Also have a rate-limiter type counter on each link, and don't send one if it is "too soon", that is: if the time now minus the time last one was was sent on the link is less than some value.
But returning to the real question: if someone is trying to work out what the hop delay times are, this is hard, because the return path can be added in and how do you separate that back out again? Also some queuing time will be mixed in, and maybe you do, maybe you don't want to see that. It all depends on what you are trying to assess: the base physical network or the current state of it, including load.