The only real problem with it is that some people don't realize how small the world can be sometimes, and how easy it is to unexpectedly encounter a previously

The only real problem with it is that some people don't realize how small the world can be sometimes, and how easy it is to unexpectedly encounter a previously burned bridge. This is especially true in specialized professions. There's nothing wrong with ghosting acquaintances or colleagues, especially those that have slighted you in some way, but it's definitely not polite to do it to friends or family, which you're connected to at a deeper level. Just know that there's a potential trade-off in that it may come back to bite you someday, such as when the person they just hired to be your new boss turns out to be your old boss.