The fact is that dynamic loads from the struts are ORDERS of magnitude higher than those imposed by the coilovers. running coilovers won't hurt a damn thing. Steeda must have a big stick up their ass to say something like that.
Ok, had to go to my fathers house to find one of his books, unfortunately I didnt find it so this is more from memory....
My father has a book at home that has a graph Mercedes Benz produced showing all of the components that make up wheel rate. If I recall correctly they actually measured loads with a data acquisition system and load cells. The contribution from springs, swaybars, friction, dampers, etc during left/right transistions.
With high damping there were some large spikes in load, but not an order of magnitude higher like you claim.
Damping force is dependent on shaft velocity. An "order of magnitute" is 10 times the original amount (two orders 100 times, etc). During the course of bump a 400lb coil over spring exerts a force of at least 1,600lbs on the strut towers. Depending on the design on the spring, a coil over spring that is compressed to 6 inches less than whatever the free length is could exert a force as high as 2,400lbs. Using your "order of magnitude" statement that would mean the damper is exerting a force of 16,000 to 24,000lbs. That is not anywhere near correct.
Using the same 400lb spring rate, if bump compresses the suspension at 3 inches in about 1 second (like a speed bump at low speed might) the increase in spring load would be around 1200lbs. The force of a damper would be around only 100lbs at 3 inches per second assuming very high damping. 100lb at 3 inches would be considered very stiff.
Hitting a 1" tall bump at high velocities, making compression maybe 1 tenth of a second assuming the same stiff damping would move the damper force into the 350 to 400lb range. Still nowhere near what the spring does.
A friend of mine runs Koni's on his GTO, I've attached a graph of his Koni adjustable shock he uses. The green line is stock, the rest are different settings through adjustment. Lower left is compression, upper right is rebound. The stiffest setting is "rattle your teeth out" stiff. At the highest shaft velocities damping forces are barely 100lbs in compression and 425 in rebound.
The shock will never exert an order of magnitude more load than the springs.
Enjoy the rest of your weekend guys!