Xiph and Mozilla have both done patent searches. The lawyers that they spent the money on told them that publicizing the results would reduce their options if they were ever sued so the only evidence they haven't found problems is that they haven't altered Theora to work around problems and that they ship it in their product, respectively.

I would assume Google (and Opera and a bunch of other companies with slightly less impressive amounts of cash and lawyers) have done the same, though I don't think they've mentioned it if they have.