4.8%. That's more than I would have thought, but it's still a small number: 95.2% of the Alexa 1000 keep AXFR disabled. Also: someone should tell some of these people not to do this.
Indeed. Keep in mind it's the top, so these are the people you really expect to keep something like that hidden. I promise you the stats are much worse further down the list, or if you do the same, but for a specific country's TLD.
