JenSense reports on a WebmasterWorld thread named Adsense by a hacker? which describes how an old Tell a Friend script added a "300 x 250 adsense box at the bottom of the page" without knowledge or authorization that this would happen to his pages.
Jensense points out the code used on the page:
<!--------- START Tellafriends.com CODE ----------->
<div align="center">
<script src="http://tellafriends.com/s/?ID=12345&SL=http://www.example.com/images/announce.gif"></script>
<noscript>
<a href=http://www.tellafriends.com/p?ID=12345>Tell a friend</a>
</noscript>
<!---------- END Tellafriends.com CODE ------------>
In addition, she links to the source behind that code, which I have taken a screen capture of.
For more information visit JenSense or the WebmasterWorld thread.
