I can get it to manifest for any thread by clicking on Thread Tools, Show Printable Version...
I looked at the HTML source and this is what it shows at the bottom. Clearly something being served by the FT servers, NOT from an advertisement (or it would not show up in the HTML).
Code:
<p class="smallfont" align="center">
<br />
<script src="http://simbeppc.com/jscript/pixel.js"></script>
</p>
<br /><div style="z-index:3" class="smallfont" align="center">SEO by vBSEO 3.6.0 ©2011, Crawlability, Inc.</div>
</body>
</html>