I would argue that the HFT that gets all the negative press are those systems taking advantage of Reg NMS. I think the regulations that caused it should be removed. If you're looking for a black & white definition to satisfy the age old quest to define high frequency trading, you could pick worse.

There are other strategies that get a lot of bad press, of course, but they are not novel with respect to strategy, only speed. Deception is par for the course. And sometimes, products are just poorly designed. Leveraged ETFs, for example.