Some basic principles of password security:
Hash it and use a salt
The people storing the password should never be able to see what the password is, just the hash
This hash should be difficult to crack
Assuming we're registering for a site that implements good password security. What if we were to take a easy to memorize password (it doesn't necessarily have to be a weak password) and performed the steps a website would do on the password and use the result as our actual password? The advantages (and please correct me if I'm wrong) of this are:
If the cracker isn't targeting this specific individual, but rather bruteforcing a login form, then the password should not be any easier to crack
You automatically get a strong password. The user only has to remember the "weak" password (think of pass phrases for SSH keys). If the user decides to use a "strong" password as the seed, and write it down, pretend they keep the paper in a locked safe guarded by armed security or something.
If the cracker determines this is the method that is used, it would take significantly longer because the hashing itself takes CPU time, and they would have to determine the hashing method used. On top of that, they would have to bruteforce the correct seed...
I know this is insecure and flawed somehow, but I would like an explanation.