title_body: Will using teabags in a Keurig cause problems?
upvoted_answer: It will not damage the machine; However, it won't brew properly.  Your tea is supposed to steep inside the water for a set period of time; but the Keurig will simply pour water quickly through it, resulting in extremely weak tea.
  
  So no, it won't damage the machine, but you will not brew your tea correctly.