Seriously, why the do we have to put up with this shit? "Google, which returns the results of your search queries over a network at nearly light speed". "Your remote control, which changes the channel on your television at nearly light speed". It is too stupid for words. Old school luddism.
All this is really to achieve front-running, executing an order after another order has been submitted but before the first order is executed. This is betting on a sure thing. It's also illegal.
Front running is when your stock broker gets an order from you but then turns around and executes an order on his own behalf before he executes yours. This is illegal because your broker has a fiduciary duty to you, his client.
It's not front running when I see an order on one exchange and then, very quickly, go make an order on a different exchange. It's not illegal because I have no fiduciary responsibility to any of the other people involved.
You have no right to execute multiple orders on different exchanges atomically.
Once orders hit the market it's public information and you can do whatever you want with it. If you can do it faster than anyone else then go you!
I suspect you won't be able to find any such source. Malfeasance by trading firms makes career cases for prosecutors.
That's not to say, normatively, that that's how things should be: obviously, prosecutors are not making much of a dent in the trustworthiness of big financial firms.
Of course everyone likes fast search results from Google... But how about when junk marketers want to use the same global network to fill people's email inboxes with spam? Most people have a problem with that, and so there's a constant fight against allowing spammers to "send untargeted bulk messages at nearly light speed".
I guess that's one way of looking at HFT: is it like email spam in that it hides real market signals under a layer of endless automatic noise? I have no idea. Seems like an interesting question though.