Some very good explanations here. Tip stalls are blamed on anything that the pilot cannot really understand/explain when the plane goes out-of-attitude. Dick explains this well when he refers to other surfaces possibly stalling first. If any flight surface stalls it not only stops creating the desired force but suddenly is a drag inducing parasite. This drag has other consequences which will often cause a sudden out of control situation. The pilot usually only observes when the wings suddely go where they should not - bad, bad, crunch! Ouch! Aerodynamics is fascinating yet few pilots ever bother to even learn the basics of what really makes their planes fly.

The original post is accurate in that the tip is not all that stalls - it is where it will start - the stalled condition of the wing will progress quite rapidly until the whole wing is stalled, unless the pilot takes corrective action.

Maintain thy airspeed less the ground rise up and smite thee mightly!