In response to various design flaws in the system and sporatic abuse I've made some changes to the way the c-index is calculated.

cindex/100=1+e^(-favorites/10)*((downloads/views+2*rating)/3-1)

Where favorites has a maximum value of 10. This has the effect of making the number of favorites less important and weighing the rating (by voting) twice as much as the download to view ratio.