title: Is it dangerous if a web resource POSTs to itself?
body: <p>While reading some articles about writing web servers using <a href="http://twistedmatrix.com/trac/" rel="nofollow">Twisted</a>, I came across <a href="http://jcalderone.livejournal.com/49707.html" rel="nofollow">this page</a> that includes the following statement:</p>
  
  <blockquote>
    <p>While it's convenient for this example, it's often not a good idea to
    make a resource that POSTs to itself; this isn't about Twisted Web,
    but the nature of HTTP in general; if you do this, make sure you
    understand the possible negative consequences.</p>
  </blockquote>
  
  <p>In the example discussed in the article, the resource is a web resource retrieved using a GET request.</p>
  
  <p>My question is, what are the possible negative consequences that can arrive from having a resource POST to itself? I am only concerned about the aspects related to the HTTP protocol, so please ignore the fact that I mentioned about Twisted.</p>