While much has been written on the vast topic of high-frequency trading (HFT), a great deal of the evidence has been contaminated by group self-interest. Furthermore, what constitutes a 'good' or a 'bad' is not clearly discussed. This paper presents an assessment of the costs and benefits of HFT and considers the more philosophical question as to what good or bad might mean here. (1) The paper formed the basis of a presentation given at JP Morgan, Sydney on 22 March 2012.