How does jQuery protect overwriting jQuery and $
<p>These variables are  located immediately after defining a local copy of jQuery in the <a href="http://code.jquery.com/jquery-1.4.4.js" rel="nofollow"><strong>jQuery source</strong></a>.</p>

<pre><code>// Map over jQuery in case of overwrite
_jQuery = window.jQuery

// Map over the $ in case of overwrite
_$ = window.$
</code></pre>

<p><em>One can read the comments and know the why... but</em></p>

<ul>
<li><p><strong>How</strong> do these lines of code do this?  </p></li>
<li><p>Would adding something similar protect my personal namespace or is there more too it deeper in the source?</p></li>
<li><p>What is an example of something bad that could happen if this weren't in the source code?</p></li>
</ul>
