It has been widely observed that the S&P 500 VIX Short Term and Mid Term Futures indices track only a fraction of the VIX spot return. For example, on 8/8/2011, in response to the US Teasuries downgrade, the S&P 500 fell 6.88%, the biggest drop in 2011 (fingers crossed!). On the same day. VIX spot jumped 40.55%, but the Short Term index only jumped 17.44% and the Mid Term index jumped 6.96%.
Overall, the Short Term index has a beta of 43% with the VIX spot, and the Mid Term index has a much lower beta of 21%. This is because the futures market is usually less sensitive than the spot to equity market movement. Furthermore this sensitivity declines with longer dated contracts.
Note that we see NO loss in correlation or diversification properties in the futures market, however. The correlation of the Short Term and Mid Term index to the S&P 500 are -80% and -78%, respectively, closely approximating the -76% corrleation of the spot VIX with the S&P 500.
Similar correlation means similar diversification;
Lower beta means higher hedge ratio.