At least the big brother of mini-Keurig that sits in my kitchen has a pretty sharp prong / needle used to open the K-cups. I wouldn't be surprised if our TSA friends didn't like it much.

On the other hand, I can imagine a tewwowist attack:

"Here, why don't you put your fingers into this strange looking hole in my coffee machine labeled >>warning, very sharp<<? Aha! This is a hijacking. If you won't cooperate, I will pierce your finger!"