Update: I was wrong, it was not a Google issue. For some reason, I had to resubmit my subscribed links XML feed to Google. I did that and now it is working again. So if you haven't yet, make sure to subscribe here and then search for link building or other typical SEO keywords.
In May 2006, Google introduced Google Subscribed Links via the Google Coop. It was confusing, but once we implemented it here, it became clearer to people how it worked. I loved it and had tons of people (thousands) sign up to see my subscribed links in the Google search results. In fact, I expanded it in April 2008. But now, it appears to be missing from the search results.
In the past, if you searched for any of the keywords that I told Google to trigger to show my pages and you were subscribed to my links, you would get those links in the Google search results. For example, if you subscribed and searched for link building, you would have seen this in the search results:
The box under seobook.com is the special subscribed links. Now, it is missing, gone, from the search results, even though, I am technically still subscribed. Where did it go? I posted this question at Google Webmaster Help and hope to get some response.
Forum discussion at Google Webmaster Help.