I never set automatic trailing stops (I could using my schwab Streetsmart pro). I set a manual trailing stop alarm (using Schwab) and then the final decision to pull the trigger or not is mine to make.
I've had too many MM's shake loose shares just to turn around and go right back up again. Not worth putting on a set-it-and-forget-it mode.
When a trailing stop trigger is alarmed on my system, I look at volume, L2 indicators and time to determine whether to pull the trigger or not. I tend to be very conservative and most times pull the trigger.
MDFI is a prime example of not being on autopilot. There are definitive MM trading patterns that show when they are just trying to scare traders out of shares (hint - one of the patterns is volume over time. The current past two hours shows sideways movement with some small volume shaking. Not working on me...I'm not selling any shares yet).