1. High-Frequency trading, by definition, done by algorithms.
2. We hear rumors or storyies of Algorithms gone wild.
3. This report blames and 'Algorithmic Trade' as the cause.
People are tempted to 'connect-the-dots' and would likely end up with an erroneous conclusion.
The differences between the algos used isn't really pertinent.
A day trader, slogging it out in front of their computer every day is very different from a floor broker trying to execute customer orders. That is the fundamental difference we're talking about here. Unfortunately, any time the markets are mentioned in connection with algorithm people instantly think "high-frequency trading", and most often they are wrong.