The only thing I could think of is that your PIN is similar to a PIN that belongs to somebody in a BBM group that might have posted his/her PIN. So people might want to join the group and type your PIN by mistake if one number or letter is wrong.
my pin is very simple - its is like 44774477 but not those exact numbers.....
In that case it would be easy for someone to just type in a bunch of numbers and get your PIN, similar to cracking a password that is not complex enough. Unfortunately, there is not much you can do, since the PIN cannot be changed, unlike a password.
