There's a lot of information about people online these days, and this is one of many "profiling" exercises that is being conducted.
Where is "hate" in America = Twitter info: http://users.humboldt.edu/mstephens/hate/hate_map.html#
The tools for trending vary in capability and usefulness. However, the social media analysis is quite insightful and does provide some insights into trends. In fact, most of the social media analysis tools are being developed by organizations to guide predictive analysis (yes, this is where Big Data comes into play). What I find interesting is that the interpretation of the data is subjective in many cases because this is not "clean data" but merely snippets of data pulled out of context (in many cases) and applied to showcase a tool or one person's perception of reality (this takes on a whole new meaning for "virtual reality"). Here's an example: The "hate in America" analysis of keywords pulled from Twitter.
How do we know that some of these discussions that included certain inflammatory keywords were not taken out of context ? The analysis would have to apply a heuristic analysis of each Tweet to assess the contextual relevance to reach a conclusion that a given Tweet should be categorized as "hateful". It is possible that the researcher (Internet Geographer) has built this level of sophistication. However, this is not a simple exercise since the analytics would need to have a large sample set of established patterns to identify a "hateful connotation". Can you imagine if a university was tagged as hateful because they were conducting a study of hate crimes or worse...if students were tweeting their thoughts on morality and/or discussing a class that discussed inflammatory references ? It does get interesting when you dig into the details to find "truth". (after all...Truth is just a perspective). The exploration and understanding of these tools will evolve over time and I'm sure that there are sites already in place to provide "watchdog" analysis over these sites but then...who's watching the watchdog ?