  Decentralized Finance (DeFi) services are moving traditional financial
operations to the Internet of Value (IOV) by exploiting smart contracts,
distributed ledgers, and clever heterogeneous transactions among different
protocols. The exponential increase of the Total Value Locked (TVL) in DeFi
foreshadows a bright future for automated money transfers in a plethora of
services. In this short survey paper, we describe the business model for
different DeFi domains - namely, Protocols for Loanable Funds (PLFs),
Decentralized Exchanges (DEXs), and Yield Aggregators. We claim that the
current state of the literature is still unclear how to value thousands of
different competitors (tokens) in DeFi. With this work, we abstract the general
business model for different DeFi domains and compare them. Finally, we provide
open research challenges that will involve heterogeneous domains such as
economics, finance, and computer science.
