<p><pre><code>    Google, MSN, Facebook, Twitter - They all already allow
    you to use anything you want for your password.
</code></pre>
This is not strictly true - while Google et al might have a large set of permitted characters, there are nearly always restrictions on length. Google, for example, requires that their passwords be at least 8 characters long. While a long password does reduce brute-force attacks and shoulder-surfing, it nevertheless is a restriction.