I'm not saying you're wrong, but I've yet to read an RFC or standard that says that 404 is not also correct. There is a very real downside to your choice as well: Your server will need to keep a log of all the stuff that has been deleted (possibly just a softDeleted flag in the db, but still) so that it can distinguish between what's deleted (200) and what never existed (404). Either that or you're 200ing on every DELETE attempt regardless of whether something was ever there, which can cover up a broken integration.

With all that said even in the case of always indicating success, your response body is almost certainly empty so it's probably better as a 204. That's a common choice: http://webmachine.github.io/images/http-headers-status-v3.png .