  Smart contracts led to the emergence of the decentralized finance (DeFi)
marketplace within blockchain ecosystems, where diverse participants engage in
financial activities. In traditional finance, there are possibilities to create
values, e.g., arbitrage offers to create value from market inefficiencies or
front-running offers to extract value for the participants having privileged
roles. Such opportunities are readily available -- searching programmatically
in DeFi. It is commonly known as Maximal Extractable Value (MEV) in the
literature. In this survey, first, we show how lucrative such opportunities can
be. Next, we discuss how protocol-following participants trying to capture such
opportunities threaten to sabotage blockchain's performance and the core tenets
of decentralization, transparency, and trustlessness that blockchains are based
on. Then, we explain different attempts by the community in the past to address
these issues and the problems introduced by these solutions. Finally, we review
the current state of research trying to restore trustlessness and
decentralization to provide all DeFi participants with a fair marketplace.
