I think the problem is primarily if you publish a REST api for commercial consumption on some level. If people depend on your REST api, the "RESTfulness" of it affords you some level of inaccuracy when documenting how things work.

But that said, I'm okay with it not following the spec as long as things are clearly documented to end users. We just went through an issue where a prominent CDN provider exposing a REST API we depend on broke REST in a very important way (i.e. NOT stateless). It's extremely annoying to try and construct clients around nonstandard APIs, and the more REST-y, the less annoying.