I'm not sure what the purpose of that site is, unless it's a joke. It isn't a database (that would be impossible), it's generating the pages in response to queries. So possibly an attempt at a scam, as in you look for your private key, and the holder of the list uses the generated pages to narrow down the possible addresses that have actually been used (there are 2^160 possible addresses, or 1,461,501,637,330,902,918,203,684,832,716,283,019,655,932,542,976). Since people have trouble putting that in perspective, there are only 2^63 grains of sand on all the beaches of Earth.
The total number of bitcoin addresses in use is so much smaller than the amount of possible addresses, that something like this is completely and utterly useless, and it would also be trivial to expand the number of possible addresses in the future. I laughed when I saw that website, cause I just know people who don't know the math are furiously putting page numbers hoping to find one
. You'll likely witness the heat death of the universe before that happens.
Yes, it seems it's a joke. Here is an interesting comment from reddit:
"I'm the owner of directory.io. This isn't an attempt at a scam. The first entry isn't "fake". It is the a private key with the value of 0. The next private key is 1, after that comes 2 etc.
The original thread has not been deleted. It is right here:
http://www.reddit.com/r/Bitcoin/comments/1rua34/all_bitcoin_private_keys_leaked/All of these keys (apart from 0) are valid. It is simply a joke. Remember when you've been told that it is almost impossible to generate a key-pair identical to somebody elses? This is a visual representation of that improbability. Look how many pages there are!
The original thread covered the fact this was a joke pretty well. No need to pretend this is a scam."
http://www.reddit.com/r/Bitcoin/comments/1ruk0z/dont_panic_directoryio_thing_is_fake/cdr18tp