Sorry if I made you nervous with the flutter flicks. As Hank indicated, flutter is serious business. I thought I'd comment about the V-n diagram presented.
The right hand vertical line is there primarily for flutter reasons. Fly into the never exceed speed range and you become a test pilot because, supposedly, no one has investigated the aircraft performance in that speed range or possibly, the flutter experts have forecast problems there and they flew as close to that point as they dared in demonstrating the aircraft's performance. If you were to fly past that line in still air, you might get away with it, then again, you might not. The actual line where bad things start to happen might not be vertical since the flutter behavior of the structure might change as positive and negative g are applied. It really isn't hard to stay below Vne as long as you keep the aircraft under good control. Just remember that there are degradations of the airframe that can cause flutter conditions to happen on the "safe" side of the Vne line (like the out of balance control surface that Hank discussed).
The top and bottom of the V-n diagram are structural limits. Pull too many g's and something has to break. Historically engineers have determined ultimate strength of the airframe (where something actually breaks) and then they set the safe operating envelope at 2/3 of that limit. You can pull more g's than the safe operating limit, it is just that when you do, you start to use up the structural lifetime of the airframe in an accelerated manner. In fighters, it is common to have over g incidents, but you try to avoid them. Maintenance personnel and engineers monitor these incidents and may flag an aircraft for additional inspections based on its "g" history. In your own personal aircraft though, you won't get this type of support, so it pays to be conservative in your flying.
The intersection of the 50 fps gust line with the safe operating g limit defines the structural cruising speed. This is just really an engineering SWAG.
(Scientific Wild *ss Guess). If you should actually fly into a 60 fps gust at the structural crusing speed, you will be beyond the safe operating g limit and causing structural damage (fatigue) at an accelerated rate, but yes, you will probably safely complete your flight. It is just that 50 fps gusts are considered far more prevalent than 60 fps gusts for normal air mass turbulence. Fly into a mountain wave rotor though and all bets are off. The SWAG wasn't intended to fit that situation.
The intersection of the accelerated stall line and the safe operating g limit normally defines the maneuvering speed. In this chart, the maneuvering speed is defined slightly higher, ie up to a slightly higher g load than the safe operating limit. The maneuvering speed is considered the fastest speed that you can bring the stick back firmly and the aircraft will stall at a g level that will not cause airframe damage. One caution though, rolling maneuvers that result in a stall at maneuvering speed will apply excessive g because the load is not evenly distributed.
What do you use the maneuvering speed for? Simply put, maneuvering speed defines the top of the airspeed range where you can safely "horse" the aircraft around. If you pull too hard, the wing will stall before g becomes excessive. In effect, the stall becomes a 'safety valve' to relieve structural stress. Just remember that the V-N diagram is normally not symmetric and what you can do with positive g is different from the negative g limits.
Should you fly into a mountain wave rotor, you will probably experience gusts from
all directions that are beyond the 50 fps figure. It is a sensation akin to being thrown into a cement mixer. In that case, a speed significantly below your maneuvering speed will be needed to stay intact. Not an experience I would want to repeat.
As you continue to decelerate along the V direction on the V-n chart you encounter your level flight stall speed. You can fly slower, but it won't be in steady state flight, more like a parabolic arc.
The intent of the above tour of the V-n diagram is to give a better understanding of the use of the diagram from a piloting viewpoint. I hope it is helpful.
Sid