  A growing body of literature is aimed at designing private mempools in
blockchains. The ultimate goal of this research is addressing several phenomena
broadly classed under MEV with sandwich attacks as the canonical example. The
literature has primarily viewed MEV as a problem arising from oversights in
distributed systems and cryptographic protocol design and has attempted to
address it with the standard tool sets from those disciplines. This paper
argues that the impact of private mempools on markets and agent incentives
renders analyses that do not consider the economic lens incomplete. The paper
presents several observations across blockchains and traditional finance to
justify this argument and highlight specific dynamics for future study.
