I have been using Zemanta with great satisfaction for at least the past 18 months. Sometime after the last update, it simply stopped working on my site. My dashboard shows that it is installed and everything is OK - but it just isn't. I see no related posts, no tags, no nothing.
I have tried deleting and re-installing, but it makes no difference. On this WordPress site - I simply get no input from Zemanta at all.