"Supplemental Results" in Google SERPs

Some URLs are tagged as "Supplemental Result" and look feed driven

[bostonBeans]

Has anyone else seen a result in Google that has "Supplemental Result" noted after the page size and before the cached link? I was doing a search today and saw this for the first time:

Query [google.com]

There are a few results on that page marked with the supplemental tag. Both are from sites that seem like logical participants in feed programs and the nature of the content lends itself to feed based submission.

Does anyone know where this data would be coming from? Doesn't seem like a fit for Froogle. Are they taking local feeds?