People have this idea that short sellers are market manipulators who conspire to wipe out innocent day traders' life savings and trigger mass layoffs with the stroke of a pen (hence the term "financial terrorism," which is absolutely comical in its hyperbole but used with complete sincerity by the anti-short crowd), but like tines said, it's a risky business that requires lots of research that frequently goes nowhere with limited upside and uncapped potential losses. The amount of times they and other short sellers publish damning evidence on a company only for the stock to shoot back as soon as the company releases a "nothing to see here" non-response really shows the difficulty in making money in the space (and how much people want to bury their heads in the sand).
Given the regulatory environment we are heading into, I expect short selling will become an even riskier business since the SEC isn't going to be prosecuting fraud anymore (or rather, they'll be doing even less than they are now), making it much easier to sic the lawyers on firms like Hindenburg. Even though this isn't their stated reason for bowing out, I wouldn't be surprised or hold it against them if it was a factor.