A few years ago, my then-employer (a smallish company, < 150 employees) had to deal with an Oracle compliance audit. I was shocked at the time to learn that there are companies (like Palisade Compliance mentioned in this article) that specialize in Oracle license compliance. We made it through just fine (in fact I believe we managed to get a small refund!), but having been through that (though not in any way directly…
When I started, I asked about licensing while setting up a new production server and the CTO admitted they were under licensed and were planning to true up licenses next quarter, but over a year went by and they never did. I suggested that they work on porting to Postgres or MySQL/MariaDB and get off Oracle (or at least consolidate into fewer servers to reduce the socket count), but they never had the time to do that.
The company went out of business shortly after the bill from Oracle came due (not sure if Oracle ever got any money). I'd already left by then since I saw the writing on the wall -- as soon as they stopped providing snacks in the break room and the coffee switched from Peets to Folgers, I knew they were running out of money.