Application Programming Interfaces (API) are a necessity in today's fast paced business community. An API can encourage mobile application, web application, and desktop development by your most passionate users, partners and the public.
Even with all this value many businesses don't have time or resources to dedicate to developing, marketing and managing an API.
If you are fortunate enough to have a passionate user base and / or offer a extremely valuable tool, you may generate the attention of rogue API developers.
Recently an innovate hacker Ronnie Roller
developed an unofficial API for Hacker News
. The popular tech news site hadn't launched their own API and apparently Ronnie saw the value in developing himself.
This is a great example of someone outside of a company developing what I would call a rogue API that extends the value of a company and its technology so much that it can gain the attention of the company and be officially endorsed, as Paul Graham did with Ronnie's Hacker News API
I think you will see more rogue APIs being developed in the future.