What is data governance? According to Wikipedia, “Data governance is an emerging discipline with an evolving definition”. That is, they don't know either. (Or, since Wikipedia is crowdsourced, I guess I should say we don't know.)
Today, data governance means different things depending on the context of the speaker. But I think the growing use of the term points toward a significant cultural shift in organizations. It's the sense that data has been accepted not just as a resource, but as a resource with potentially volatile qualities. Topics that attract “governance” are those that are likely to go wrong if left to their own devices.
The emergence of a discipline loosely known as data governance indicates increased awareness that data is a business issue, not (just) a technical one. Wikipedia