Note that this page includes jQuery 1.2.6 in case you want to test execution of a requires-newer-than-1.2.6 bookmarklet. If you want to do version testing, click here for a good starting point.
This bookmarklet, requiring jQuery 1.4.4:
(drag this to your bookmarks bar or right-click and add to bookmarks)
Was generated from this code:
user2="";if($(".twitter-anywhere-tweet-box-editor").length){user1=extractAt($(".twitter-anywhere-tweet-box-editor").val());user2=$("#screen-name").text().replace(/[\s\xA0]+/g,"")}else{if($(".tweet.permalink-tweet").length){user1=$(".tweet.permalink-tweet").attr("data-screen-name");user2=extractAt($(".tweet-text.tweet-text-large").text())}else{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=?";alert(url);$.getJSON(url,function(a){if(a){alert(commonFollowers(a))}});function extractAt(a){splitText=a.split(" ");if(splitText[0].substring(0,1)=="@"){return splitText[0].replace("@","")}}function commonFollowers(b){var a=new Array();nref="nodes_referenced_by";followers=new Array();for(u in b.nodes){a[a.length]=u.replace("http://twitter.com/","");lfollowers=new Array();cofriends=new Array();for(i in b.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};