I thought Google Alerts were to tell you when specific phrases were encountered, like "MyMostlyUniqueFullName" or "MyCompanyName". "Recipe" doesn't seem that useful -- or at least doesn't match my M.O. for Google Alerts.
I'm guessing that most Google Alerts are "vanity alerts," as your examples suggest. The putative decline of the service could thus fit with the idea that such functions are meant to be subsumed by Google+.
