In studying the increasing role that opaque, algorithmically-driven systems, such as social media feeds, play in society and people's everyday lives, user folk theories are emerging as one powerful lens with which to examine the relationship between user and algorithmic system. Folk theories allow researchers to better see from users' own perspectives how they understand these systems and how their understanding impacts their behavior. However, this approach is still new. Methods, interpretation, and future directions are up for debate. This panel will be an active discussion of the contribution of folk theories to HCI to date, how to advance a folk theory perspective, and how this perspective can bridge academic and industry study of these systems. Our panel gathers key folk theory HCI researchers from academia and industry to share their perspectives and engage the CHI audience.