If you publish your hub anywhere else, even if it is published first on HubPages, some human (I am not sure they really mean that) might spot it and declare that your work is a duplicate and will ban it until you rewrite it.
I had a Hub that I published on HubPages. It was picked up by an United Kingdom newsletter that I have written for in the past (no pay) , and it ran two days after being on the Hub.
So the newsletter duplicated the Hub, but my Hub was banned. I reworked it twice, but could never meet their approval. I just removed it. I do not see why we can link our hubs to Facebook, insert them in our Blogs but not allow them to go anywhere else. It is the one big complaint I have with HubPages. I do not think that rule is fairly enforced.