What are some gray area industries you know?

I was a developer at a blockchain company based out of Seattle Washington. We did an ICO (still unsure if it was legal), we built cool shit, I left for a better job offer, learned a lot about blockchain development, dapp architecture, solidity coding, erc token standards, and the legal spaghetti that crypto companies inevitably find themselves in if they are based in the U.S.

I always wonder about the places that pay for scrap light metals, open to the public. This seems like an industry that has to deal with a lot of sketchier people, that drive up in a pickup full of materials whose provenance is impossible to determine. I'm certain that recycling is legal, I just wonder how much the recyclers have to ignore from their suppliers.

Web search? Because it requires scraping websites and redistributing their content in the form of text excerpts and images on search result pages. I mean, isn't that technically against copyright?

Payday loans, the vaping industry, poultry and cattle farming, pharmaceuticals, electronics manufacturing... I could keep going, but most industries have rough spots somewhere along the chain.

weed industry, ignoring federal law