Probably There, Definitely Not There - The Magic of Bloom Filter
When signing up for an email or to a website do you remember the exhausting procedure of selecting a username? First, you try with something simple like your first name or last name. Unless you have a really unique name, good luck with that. Next, you append your birth year to it. Still no luck? I am sure you have tried adding your phone number too. By this time, you already start loathing your username.