Yes, iLike lost about 70% of their traffic. People now think iLike is just a part of the facebook. They'll be in similar situation as the author of the app discussed in the article.

Problem with monetizing facebook apps is that not even facebook can monetize its users through ads: http://valleywag.com/tech/advertising/facebook-consistently-the-worst-performing-site-242234.php

Maybe virtual gifts/items will help facebook's bottom line? Who knows... but clearly advertising might not be the holy grail.