This is the javascript that you can find in www.twitter.com (just click to see the source code) I have just reformatted it for clarity:

if (window.top !== window.self) {
  document.write = "";
  window.top.location = window.self.location;
  setTimeout(function() {
    document.body.innerHTML = '';
  }, 1);
  window.self.onload = function(evt) {
    document.body.innerHTML = '';
  };
}

now I understand this trick is to prevent other sites to wrap twitter in other iframes. but what I want to ask is do we really need all of this code ? what's the need of setting a function to execute in 1 millisecond, one to execute at 'onload' and one now.

is that paranoia or is it really worth ?

Many THanks in advance Reg