Most likely because there have been some alarming failures of automated traders, such as the 2010 "Flash Crash" or the April Flash Crash caused by a Twitter hoax. From a layman's perspective, it seems like all the regular problems of speculation with the added benefit of trades taking place faster than any human regulator could react. So far there hasn't been any serious damage but it's not clear to me whether that's a point in the traders' favors or just blind luck.

Of course, this isn't a Friendliness issue so much as a competence one and I'm fa... (read more)