In a lot of older web applications as well as newer RESTful services I've seen it fairly common to have identifiers such as user and order IDs just being an auto incremented primary key from the database. This approach has the problem of revealing your total number of users/orders in a certain time period. Information your competitors could use against you!
When I had to use Erlang for the very first time it was a brand new language and I was in collage. Back then Erlang did not have a logical not function so we had to define our own in order to make our code readable. At least given the knowledge me and my lab partner had at the time. So the other week I had a deja vu moment since I had a Task<bool> that I wanted to negate. At first it felt real weird and I ended up solving my problem in a different way. But then I started to think.