My take on stops:
1. Good insurance policy against unknown loss.
2. Exit method, rarely the best exit method unless you just want to keep it simple.
3. Biggest misuse is outright long / shorts that rely on stops for exit and have the
same arbitrary values. Longs and shorts typically vary quite a bit in volatility, and timescale.
Rough generalisation, but shorts are rarely optimal with a trailing stop (Intraday),
whereas longs can benefit from trailing stops - with the caveat that they are not the primary exit method.
The above can work, but is far from optimal.
4. Mental stops, again perfectly ok with position trading for instance.
Having said that, I personally think there is merit in a hard outlier event stop at
the very least.
5. A wider stop is pretty much essential with a tighter stop limit order.
If the limit order doesn't get filled you have insurance.
6. Hardware failure insurance - say your brokers servers go down, phone lines are jammed.
Now imagine that happens in the middle of something like the japanese reactor
disaster in early 2011 during rollover time.
You will get shafted bigtime - search this site for tales of exactly that.
7. Then there is your own PC, internet connection and power, if that fails
without a stop again you are screwed until you get it sorted or get through on the phone.
8. Generally most of the above mainly applies to mildly leveraged intraday trades.
Unleveraged position trades can get away without.
9. Make sure if you do use a stop it is one on the brokers server.
Sounds obvious - mainly that applies to platforms that simulate OCO within the platform.
Just my personal take on stops