SO TRUE!
I've seen two inexpensive WM high polished spinners shake a plane so hard that the tip was a blur on both a two stroke and YS 110S. One ten second full power run and the engine mount screws were loose....the threads into the blind nuts even had blue locktite! I inspected the one I had and both the back plate AND the spinner were waaaay off balance. If you happen to have a bad one of these, is could very well kill your plane if you manage to takeoff with it.

I've never had problems with Tru turn or Dave Brown spinners.