It seems that VIX futures could be a great hedge for a long-only stock portfolio since they rise when stocks fall. But how many VIX futures should I buy to hedge my portfolio, and which futures expiration should I use?
VIX measures volatility. It doesn't always go up if stocks go down.
VIX also has a lot of complexities that make it a less-than-ideal hedging tool if you're buying a VIX ETF.
http://vixandmore.blogspot.com/ goes into it at length and can probably also answer any questions you have about the VIX as a hedge.
To expand on what @barrycarter said, the VIX is better as a hedge against kurtosis, not against downward movements.
We just made a video on CBOE-VIX Hope you like it https://vimeo.com/41915075