whoCanSeeThisTweetBookmarklet.js

  user2 = '';
  if ($('.twitter-anywhere-tweet-box-editor').length){
	  // New Twitter textarea tweet entry
	  user1 = extractAt($('.twitter-anywhere-tweet-box-editor').val());
	  user2 = $('#screen-name').text().replace(/[\s\xA0]+/g,'');
  } else {
	if ($('.tweet.permalink-tweet').length){
	   // status page when logged in 
	   user1 = $('.tweet.permalink-tweet').attr('data-screen-name');
	   user2 = extractAt($('.tweet-text.tweet-text-large').text());
	}else{
		//status page when not logged in
		user1 = $('.tweet-url.screen-name').text();
		user2 = extractAt($('.entry-content').text());
	}
	
  }
  gtyp='edi';
  url='http://socialgraph.apis.google.com/lookup?q=http://twitter.com/'+user1+',http://twitter.com/'+user2+'&'+gtyp+'=1&callback=?';

  
	  $.getJSON(url,
   function(json){
     if(json) {
         alert(commonFollowers(json));
	 }
   });
function extractAt(aMsg){
  splitText = aMsg.split(' ');
  if (splitText[0].substring(0,1)=='@'){
	  return splitText[0].replace('@','');
  }
}
  
function commonFollowers(json){
  var name=new Array();
  nref='nodes_referenced_by'
  followers=new Array();

  for (u in json['nodes']) {
    name[name.length]=u.replace('http://twitter.com/','')
	lfollowers=new Array();
	cofriends=new Array();
	for (i in json['nodes'][u][nref])
		lfollowers[lfollowers.length]=i	
	followers[followers.length]=lfollowers
  }
  for (i in followers[0]){
    if (followers[1].indexOf(followers[0][i])>-1){
	  cofriends[cofriends.length]=followers[0][i]
	}
  }
  output = user1+': has '+followers[0].length+' followers'; 
  if (user2 != '') {
    output +=  ' of which '+cofriends.length+' followers in common with '+user2;
  }
  return output
}