Yoma, Chapter 3, Mishnah 11. The previous mishnah listed a group of people whose deeds and improvements in the Beis HaMikdash were praiseworthy and remembered favorably. Our mishnah lists, in contrast, those whose deeds were considered negative and who are remembered to their discredit.
"V'eilu l'gnai":
"Shel beis Garmu" - the family of Beis Garmu refused to teach others how the lechem hapanim was made. Preparing the lechem hapanim was difficult work, since its walls stood straight up and it could easily fall apart, and they had a method for keeping it intact.
"Shel beis Avtinas" - they refused to teach anyone how the ketores was prepared.
"Hugras ben Levi" - a Levi who knew a special chapter of song, meaning that he knew how to sing in a particularly beautiful way using a certain technique, and he refused to teach it to others.
"Ben Kamtzar" - he refused to teach the art of writing. He would hold four quills between his five fingers, and with them he could write the four letter Name of Hashem all at once - and this method he refused to teach.
The first group and the last group:
The mishnah concludes: "Al harishonim ne'emar: 'zecher tzaddik livrachah'" - about the first group the verse in Mishlei is applied, that the memory of a righteous person is a blessing. "V'al eilu ne'emar: 'v'shem resha'im yirkav'" - the name of the wicked, of evil people, will rot.
Who exactly are those remembered to their discredit:
We need to consider precisely whom the mishnah is referring to. The Gemara mentions that Beis Garmu and Beis Avtinas, who were involved with the lechem hapanim and the ketores, gave the Sages a reason for their refusal to teach: they were afraid that a person who was not upright would learn the method and use it for idol worship. This raises the question of whether the Sages accepted this explanation or not. The Gemara also brings a beraisa stating that in practice all of them had a justification for their conduct - except for ben Kamtzar, who had no excuse at all.
In summary: This mishnah lists four who are remembered to their discredit - Beis Garmu regarding the lechem hapanim, Beis Avtinas regarding the ketores, Hugras ben Levi regarding the chapter of song, and ben Kamtzar regarding the art of writing - all of whom withheld their knowledge from others, and about them it says "v'shem resha'im yirkav," in contrast to "zecher tzaddik livrachah" which was said about the first group. We also examined the words of the Gemara regarding the reason they gave, and the fact that ben Kamtzar alone had no excuse for himself.