Social index changes lead to sudden price fluctuations. To be fair, in the majority of cases, the price goes opposite of the general market mood (but it depends severely on the phase of the market), therefore, if you are one to counter-trade chat room opinions - this tool is first to display the market mood, be it bullish, bearish or neutral.
The market order flow indicator, located right next to the social index indicator, is the ratio of market buy : market sell orders. (i.e.: current short-term trend).