Why 1337 sucks.

The obvious problem with this is its ambiguity. If I write 600613, how do you know if I am saying 'Google' or 'Boobie'? Saying 'Boobie' when you mean 'Google' could get you into trouble, depending on what company you are among.

1337 has an even bigger problem, and that is its unintelligibility. More on that later.