Code adds tag cloud feature to Giant Bomb chat room (http://www.giantbomb.com/chat/). Should be able to copy & paste this into your browser's console to try it out on your own. Otherwise, let's see if this feature is added at some point.

gb-chat-cloud.js

// Set global variables to be used when switching between auto/manual refresh & their interactivity
origInitialTagCloudH = '80px';
initialTagCloudH = origInitialTagCloudH;

// Fuction to update tag cloud... simply execute updateTagCloud() when you want a fresh cloud
function updateTagCloud(){
	// Get text from chat
	text = '';
	$('#conversation-main .msg').each(function(){text+= $(this).text()+' ';});
 
	// Get word list sorted & labelled based on frequency of use
	var words = (function(){
		var sWords = text.toLowerCase().trim().replace(/[,;.]/g,'').split(/[\s\/]+/g).sort();
		var iWordsCount = sWords.length; // count w/ duplicates
		// array of words to ignore
		var ignore = ['the','a','an','I','i','i\'m','it\'s','me','myself','my','we','ourselves','ourself','ours','our','you','yourself','yours','your','yourselves','y','he','him','himself','his','she','her','herself','hers','it','itself','its','they','them','em','themselves','theirs','their','aboard','about','above','absent','across','after','against','along','alongside','amid','amidst','among','amongst','around','as','aslant','astride','at','atop','barring','before','behind','below','beneath','beside','besides','between','beyond','but','by','despite','down','during','except','failing','following','for','from','in','inside','into','like','mid','minus','near','next','notwithstanding','of','off','on','onto','opposite','outside','over','past','plus','regarding','round','save','since','than','through','throughout','till','times','to','toward','towards','under','underneath','unlike','until','up','upon','via','with','within','without','anent','betwixt','circa','cum','per','qua','re','sans','unto','concerning','considering','regarding','but','except','plus','save','ago','apart','aside','away','hence','withal','and','nor','or','yet','so','both','either','neither','not','also','will','would','got','shall','should','may','might','can','could','must','have','ought','had','dare','need','do','well','still','however','nevertheless','otherwise','moreover','addition','furthermore','besides','first','second','finally','thus','anyway','then','too','while','although','though','because','unless','since','is','that','be','this','if','what','are','how','all','put','just','way','one','has','was','some','when','more','only','something','see','there','very','don','things','other','any','each','really','even','much','same','different','does','many','most','once','thats','cause','ok','here','out','ve','ll','which','http:','-',':','.','?'];
		ignore = (function(){
			var o = {}; // object prop checking > in array checking
			var iCount = ignore.length;
			for (var i=0;i<iCount;i++){
				o[ignore[i]] = true;
			}
			return o;
		}());
		var counts = {}; // object for math
		for (var i=0; i<iWordsCount; i++) {
			var sWord = sWords[i];
			if (!ignore[sWord]) {
				counts[sWord] = counts[sWord] || 0;
				counts[sWord]++;
			}
		}
		var arr = []; // an array of objects to return
		for (sWord in counts) {
			arr.push({
				text: sWord,
				frequency: counts[sWord]
			});
		}
		// sort array by descending frequency | http://stackoverflow.com/a/8837505
		return arr.sort(function(a,b){
			return (a.frequency > b.frequency) ? -1 : ((a.frequency < b.frequency) ? 1 : 0);
		});
	}());
	(function(){
		var iWordsCount = words.length; // count w/o duplicates
		// Assemble array containing the words & their frequency (already sorted)
		wordArray = [];
		for (var i=0; i<iWordsCount; i++) {
			var word = words[i];
			wordArray.push([word.frequency,word.text]);
		}
		highestFrequency = wordArray[0][0]; // Get the highest frequency (to be used to size words)
		//console.log(wordArray);
	}());
 
	// Remove old tag cloud
	$('#tag-cloud li').remove();
	// Populate with latest set of words
	for (var i=0; i<wordArray.length; i++) {
		word = wordArray[i][1];
		frequency = wordArray[i][0];
		relativeFrequency = frequency/highestFrequency;
		if(relativeFrequency>=0.1 && word != '') // Only show if it's greater than a certain relative freqeuncy (prevents a mile long list of once-used words), and make sure the word isn't blank (comes into play when the chat's still loading)
			$('#tag-cloud').append('<li style="font-size:'+relativeFrequency+'em;">'+word+' <em>('+frequency+')</em></li>');
	}
	// Make height interactive (only show full list on hover)
	tagCloudH = $('#tag-cloud').css('height','auto').height();
	$('#tag-cloud').css('height',initialTagCloudH).on({
		mouseenter:function(){
			$(this).stop().animate({height:tagCloudH},400);
		},mouseleave:function(){
			$(this).stop().animate({height:initialTagCloudH},400);
		}
	});
}

// Create placeholder for tag cloud
$('#history').prepend('<button id="auto-refresh-tag-cloud" class="btn" style="float:right;">Enable Live Cloud</button><button id="refresh-tag-cloud" class="btn btn-primary">Get Fresh Cloud</button><ul id="tag-cloud" />');

// Add styles to head (done here to simplify/centralize edit)
$('head').append('<style>#tag-cloud { clear:both; margin:0.1em 0; font-size:4em !important; } #tag-cloud li { display:inline-block; border:none; margin:0; padding:0.2em 1em; box-shadow:none; } #tag-cloud li em { font-size:0.7em; opacity:0.2; cursor:default; user-select:none; -webkit-user-select:none; -moz-user-select:none; -ms-user-select:none; }</style>');

// Initiate Tag Cloud
updateTagCloud();
setTimeout(function(){updateTagCloud();},5000); // Refresh after chat has loaded.

// Refresh Tag Cloud on Button Click
$('#refresh-tag-cloud').on('click',function(){updateTagCloud();});

// Toggle Auto-Refresh on Button Click
autoRefreshTagCloud = false; // Default
$('#auto-refresh-tag-cloud').on('click',function(){
	if(!autoRefreshTagCloud){
		tagCloudRefresh = setInterval(function(){updateTagCloud()},1000); // Refresh every second
		$(this).text('Disable Live Cloud');
		autoRefreshTagCloud = true;
		initialTagCloudH = 'auto'; // Show all of the tags
		$('#refresh-tag-cloud').hide(); // Don't need the manual refresh anymore
	}else{
		clearInterval(tagCloudRefresh);
		$(this).text('Enable Live Cloud');
		autoRefreshTagCloud = false;
		initialTagCloudH = origInitialTagCloudH; // Go back to the show/hide behavior
		$('#tag-cloud').stop().animate({height:initialTagCloudH},400);
		$('#refresh-tag-cloud').show();
	}
});

View a screenshot of it!
The ignored words could use some tuning. Took a common word list & did some fine tuning, but can be polished further.

Updated it so now there's a button to enable/disable auto-refresh! Screenshot to prove it.