Like @WindsCurve, no one shows up in my block list. I know I accidentally used the block icon to ignore some participants whose background noise resulted in them dominating the main screen from the podcaster. I doubt anyone blocked me. Like most of the other participants in the hangout, I wasn't sending audio or video, just listening and text chatting, and only chatted a city name. Now, I am blocked from the hangout, and had no advance warning that would happen.
For the future, it would be nice to have a warning upon clicking the "cancel" icon that it's not to temporarily ignore, but will prevent me from returning to the hangout.