sorry for late replies guys, we got low karma and can't reply as often/fast as we'd like. We got some countermeasures planned to avoid inflating user numbers. Kind of been feed to us by interested startups :)
The reason is on the "about us" link on the site ;).
we needed it, couldn't find it, so we we started working on it and launched a landing to test if this pain was only ours. apparently it's not. Posted it in a few italian startup groups and shared it with a few friends. It went by itself from there, we found ourselves on product hunt, than here in HN...it just...happened :)
"We got 5000 new users in the first hour!"