If I am not mistaken, there have been many cases where prior art was available (and in some cases quite well known within the field) but did not come to the att

If I am not mistaken, there have been many cases where prior art was available (and in some cases quite well known within the field) but did not come to the attention of the examiner (or the examiner did not recognize its relevance), and the patent was granted anyway. In fact, there was one such case on the HN top page today. https://news.ycombinator.com/item?id=31881973 https://news.ycombinator.com/item?id=31881973 Once that happens, getting it revoked is no easy task.