There seems to be a mix of legit use cases and mania going on with the NFT craze. I can see use cases like NBA Top Shot being legit, here you have essentially the digitization of trading cards (a proven collectable market) backed by a major sports league. The top shot "moments" have some unique advantages over traditional trading cards in that they can't be damaged/stolen/lost, can be traded instantly online, and may be more interesting to fans since they are videos vs pictures. You can see the transaction history of a moment, and in some cases NBA players themselves are trading them adding to the value for die hard fans. Being backed the NBA and unique content created specifically for the purpose of trading via NFT, I could see them having a long term value & market https://www.nbatopshot.com
Then there are ideas leaning more towards mania, essentially trying to make "NFT for X" by adding a token to every piece of digital data. For example, NFTs for tweets: https://v.cent.co/tweet/20 (current bid is 2.5 million for Jack Dorsey's first tweet). I suppose these tokens have value as long there is a market for them, but at certain price points I question if they can sustain long term and if they are more trying to cash in on the mania.
Debate on this topic here: https://news.ycombinator.com/item?id=26370866