  Non-Fungible Tokens (NFTs), digital certificates of ownership for virtual
art, have until recently been traded on a highly lucrative and speculative
market. Yet, an emergence of misconceptions, along with a sustained market
downtime, are calling the value of NFTs into question. This project (1)
describes three properties that any valuable NFT should possess (permanence,
immutability and uniqueness), (2) creates a quantitative summary of permanence
as an initial criteria, and (3) tests our measures on 6 months of NFTs on the
Ethereum blockchain, finding 45% of ERC721 tokens in our corpus do not satisfy
this initial criteria. Our work could help buyers and marketplaces identify and
warn users against purchasing NFTs that may be overvalued.
