In this paper I discuss the epistemological implications of the rise of so-called “Mode 2” science. Mode 2 science is a kind of knowledge production in the context of application where knowledge production is conducted in a heterogeneous manner. Because of these features, bilateral science communications, where lay expertise has the same authority as scientific expertise, play significant roles in Mode 2 science. Features of Mode 2 (especially heterogeneity and use of lay expertise) pose epistemological questions: is Mode 2 knowledge as reliable as Mode 1?; what is the methodology used (or at least available) in Mode 2 to assure the reliability?; is Mode 2 worth the name of “science”?; if yes, what is the definition of 'science' used there? I maintain that we can enrich the philosophy of science by taking these questions seriously, and I conduct some preliminary considerations on the final question, namely the question of demarcation taking into account of Mode 2.