Wallet passphrase uniqueness (noob question) The Mycelium Wallet has created a Bitcoin wallet for me, then I've written down a 12-word passphrase for the wallet backup. However it looks like a set of words (in the Mycelium) to generate these phrases is limited - at least I've got a passphrase with one word repeated two times.

How can I make sure this passphrase is unique in our world where more than 7 billion people live?
The chances of someone "brute-forcing" or guessing your seed is extremely slim. There are more than 5 duodecillion possible combinations of twelve-word seeds. Just so you get an idea of how big that number is, it's more than 1 thousand million million million million million million possibilities.