While the transfer of the assets after a sale may take several days, the buying and selling takes place in milliseconds. If something is offered for sale at a bargain price, and 8ms later I accept while a Go user is stuck in a 10ms GC run, I get the deal, and he misses it.
If 8ms matters, aren't we talking about HFT? I'd be incredibly surprised if the rest of the industry ran on that kind of timing. Doesn't it take minutes to hours for a trade to happen if, for example, I click buttons on E-Trade or call my broker?
FYI, if you trade on ETrade, the slower their infrastructure is, the harder it is for you to buy/sell large amounts of anything. Why? When you pull the trigger to buy 100000 shares of xfoobarx, the market will see that and react accordingly. The faster you can actually buy those shares, the less time the market has to react, and as a result, you'll manage to succeed in making more of the trades you want.
Like it or hate it, electronic trading is the natural progression of the markets, just like the car eclipsed the horse. Low latency in trading applications affects me when I move my 401k as much as it affects the big electronic trading firms. Thinking it doesn't affect you is a mistake :)
When you, or a hedge fund, or any other market participant, decide to sell or buy a security, the trade is submitted to a broker. That broker may submit the trade to the floor, an ECN, or market maker, and so on. Only in very specific cases -- particularly an ECN to a specific exchange where it might have a spread with a regional exchange, is timing so critically important.
But for 90% of those trades, it's a block limit order that sits on the order book until it's filled.
For many trades this is irrelevant. For those where it does matter, it is the very last, smallest part of the system -- the execution engine -- where timing is everything. That is the part of the system where HFT engineers are building hyper-speed interconnects and optimizing every single instruction, but it is not relevant to the majority of the stack.
Delays everywhere else in the system are largely meaningless -- yeah prices may have changed slightly, but unless you've mastered market timing (which no one has), it will generally even out and is irrelevant.
