Hi All
Yes, we are experiencing the same issues recently with ptr-requests forwarded to the iana blackhole nameservers.
# dig -x 10.0.0.100 @blackhole-1.iana.org
Traceroute? :) Those nodes are anycasted. See previous answer or google AS112.
...and when you are trying to debug AS112 stuff you normally also want to try to run this:
--snip # dig +short txt hostname.as112.arpa "Unique IP: 91.206.52.250 / 2001:7f8:24::fa" "See http://as112.net/ for more information." "AS112 at SwissIX, http://www.swissix.ch, Zurich, Switzerland" --snap
This will surface the name of the node you are ending up with. Running a traceroute will probably not help so much because, as you already correctly stated, this is an anycasted ip-address. It may point you into the right direction, but it might as well misguide you.