Meno: I think I am wrong about why they did it. I read a couple things and maybe misinterpreted it.
From Kosher Today:
“According to Rabbi Moshe Elefant, COO of the Orthodox Union (OU) Kashrus Division, certified kosher K-Cups used in the machines no longer have the OU symbol on the individual cups although they remain on the boxes that they come in.
Thus, a kosher consumer who randomly finds a K-Cup without a box may inadvertently be using a non-certified K-Cup causing one rabbi to suggest that the user of such a Keurig machine might have to refrain from using the machine for 24 hours, run a kosher K-Cup through the machine and even kosher the two metal pins.” (Kosher Today)