It's very common. I hate it. It's fully accepted. I hate it. Hate, hate, hate. It's almost certainly in the dictionary--yes, ahdictionary.org says "3. Contribution of information or a comment or viewpoint: a discussion with input from all members of the group." I hate it. I would never use it myself, because I hate it. It's a misappropriation of a technical term. Did I mention that I hate it? Because I do. And I don't like "feedback," either.