In most cases an API is used to increase the visibility of the company and its services. In some cases, it can be an additional source of income based around usage (free up to a certain number of hits). I think it is meant to be a mutually-beneficial or symbiotic relationship. I don't think that there are conflict of interests as it is a public API. It would be in the terms of use if it was, and you can elect not to use it.