<p>Questions are usually <a href="http://meta.stackexchange.com/questions/52764/what-is-a-protected-question/52765#52765">protected</a> when there is a slew of non-answers being posted as answers.</p>

<blockquote>
  <p><a href="http://blog.stackoverflow.com/2010/06/new-protected-question-status/">Protected</a> questions have the additional restriction that <a href="/privileges/new-user">new users</a> are not permitted to answer the question.  Unlike <a href="http://meta.stackexchange.com/questions/22228/what-is-a-locked-post">locked</a> questions, they can still be edited, commented on, and voted on.  You can even vote to close them.</p>
</blockquote>

<p>Examples include:</p>

<ul>
<li>spam</li>
<li>Thanks!</li>
<li>I have the same problem, how can I fix it?</li>
<li>spam</li>
<li>I'm too lazy to get rep so I write a comment, so here's an a non-answer for the mods to remove.</li>
<li>I haven't read the FAQ, so here are more details for my question, posted as answer.</li>
<li>spam, spam and more spam</li>
</ul>

<p>Usually in such cases, the question will be protected by a mod, a high rep user (15k and up). The <a href="/users/-1">Community user</a> will automatically protect any question where three answers posted by <a href="/privileges/new-user">new users</a> have been deleted.</p>

<p>You cannot simply trigger protection via a flag, however, as a real person must accept your request and follow through with protecting the question. However, if you believe a question should be protected, flag for moderator attention and someone will look at it.</p>