In a statement released on 18 march, ESMA indicated that national regulators have taken big steps in improving the level supervision of HFT.
ESMA correctly stated as well that there is still room for improvement. The trading community is coming up with new technology and software on an almost daily basis and regulators are having a hard time catching up. The skills required to understand the data, the algorithms, the IT, etc do not come cheap and probably you will find the best in HFT.
Innovation is not limited to the trading community. Developments in market infrastructure, new products and international co-operation stress the available resources at national regulators even more.
Spending taxpayers money on financial markets is probably not very popular. However, the alternative is worse.
Read the full ESMA review here.