BA 737 BCN/LGW a few years back - take off roll started then stopped, then the slats set and off we went.
General practice on the airlines I fly mostly BA/EZ is to set these before the start of taxi.
If one day I notice it hasn't been done should I be up out of my seat? I think so as it would be a departure from the norm.
How do we know that pax on the Spanair noticed this and did nothing? From what I read there were quite a few staff on board as well.