Never Exceed Speed (Vne), Indicated Air Speed (IAS) and True Air Speed (TAS) are closely linked, and if you don't understand how and why, they could have an effect on your BVDs.
Flutter is a so-called aeroelastic effect that results from the springiness (elasticity of the airfoil and the surrounding air), aerodynamic forces, and inertia.
It doesn't have to be a plastic ship, either. Here's a NASA film of a Twin Comanche's empennage (note how the fuselage skin flexes just ahead of the horizontal stab).
And a Lockheed C-141 (note the tail is resonating too)
What happens if you go too fast, push the aircraft past the speed where it flutters? Here's one of Grumman Iron Work's A6 Intruders.
Why does Vne go down with increasing altitude? Because there's less air to act as a shock absorber. Because there's less resistance to the wing (or other structure) flexing, you have to reduce the forces on that structure. The only way to avoid flutter (without redesigning the wing) is to go slower.
Remember, your airspeed indicator lies. It won't tell you what your TAS or never exceed speed is. In fact, it may be a compulsive liar and even lie to you down low (click to enlarge).