1) the markets self correct much better than they used to. I think this is a positive and
2) that stop order should almost never be used. During the crash of 1987 stop orders were just coming into vogue as a sort of protection. The ides with them is that they are sell or buy orders that are in the money but not entered onto the CLOB(Continuous limit order book). Once the stock falls below their strike price, they spring into action and become orders to sell (or buy if you are stopping for short protection).
This has a downside of extending slides when markets go down because as markets fall stops get hit which adds to the selling which means more stops get hit, rinse and repeat.
Unfortunately this means that in a flash crash you'll get stopped out of your position and when the market recovers you'll wonder where your shares went.
Stop orders, just say no. Even if you are watching the markets, you'll be too slow to cancel them.