IP norms and a bit on IRBs

Via Jason Schultz in Jotwell, I learned of a great new paper by Julia Bauer et al. on community norms about copying and anticopying enforcement in the Threadless (crowdsourced T-shirt) community.  There are many interesting results, including the evidence they present of procedural fairness norms to go along with the anticopying norms.  But I'm sensitized to a separate question: part of the paper involved deliberately introducing copied designs to the community and waiting for detection and response.  Since the authors knew from their previous research on actual copying cases that community members often reacted with outrage to blatant copying, why is this (rightly) recognized by Jotwell as useful empirical evidence, while Facebook's testing of the effects of altering the newsfeed seems outrageous?  As far as I can tell, the authors do not indicate that they submitted this study to an IRB (institutional review board); I'm informed by my in-house expert that as foreign researchers they likely didn't have to.  This experiment seems a lot closer to human subjects research than what Facebook did.  Is it outrageous?