re: Flight from San Francisco forced to divert to Denver after plane's wing came apart

Former aircraft quality guy here

Damage looks to me like a bird strike. Not sure if the slats on the leading edge are composite or not on this model but the damage, while ugly, doesn’t seem to be bad enough for an IFE. (In flight emergency)
Slats are rear of the engine intakes so no real chance of FODding an engine. Possibly damaged pieces could affect the horizontal stab on that side of the plane, but probably not to the point of being a true issue.
Biggest issue would probably be at landing when slats are deployed as plane slows down but may not have been consequential enough for flight crew to even notice.

To answer one posters question about maintenance these birds are checked at certain intervals of flight hours. Certain inspections are done at different periodic inspections, with frame age and past issues taken into account. But virtually all have fatigue stress/cracks in certain areas of the plane. Eddy current or Ultrasonic inspections are then used to check things such as skin fatigue, especially around rivet holes. Cracks usually stop-drilled at the end to slow/stop propagation of the defect until it crosses certain thresholds, at which time they are repaired or replaced. Same with x-ray inspections on the birds frame internals.