why spikes under speakers???

Some spikes are more cone shaped than others. Cones run one way when it comes to vibration. They 'drain' vibration from the speaker cabinet and dont permit vibration from traveling up from the floor. Thats why with cones under components and stands you get less vibration.
As for speakers moving, I have seen speakers and subs "walk". Its the vibration of the cabinet that you are trying to reduce. A drivers motion will be more precise if its 'working against' a solid stationary baffle to start and stop from , as opposed to a vibrating baffle. Spikes ususally improve the sound by giving the drivers a less resonant platform so they work better and also by reducing the sound you may hear from the cabinet itself.

The idea that a cone can act to decouple and block vibration sounds no less absurd than the notion that cones can channel vibration. If the large surface area of a cone is in contact with the chassis of a component and the componenet is vibrating due to 'airborn vibration', the cone will vibrate also. I submit cones can reduce vibratoin in the chassis even if it is resting on an decoupled shelf. If this is so, then where is the vibration going? Is it dissapated as heat at the cone's small contact point? Or do you think that the only effect is decoupling?
I have seen cones reduce energy in a component that was sitting on a decoupled shelf. I dont think my idea is absurd.

Ok, maybe 'drain' was the wrong word, 'transfer' might be more accurate. Please take a minute to consider this experience I had.
A friend had a TT that had three relatively flat aluminum cones that served as feet. The flat side makes contact with the flat bottom of the turntable. The turntable sits an a welded target stand. He put on a classical lp and during a loud passage that had a lot of bass the cartridge mistracked. He said, "that never happened before". I checked the cone footers and found that he had absentmindedly put them facing up, not down. We flipped them over and replayed the passage. Of course the tracking problems were gone. You could feel with your fingers a huge difference when you touched the TT base. We removed the cones and placed the TT on a folded over towel and tried it again. We could feel more vibration in the TT base than when the cones were under it (correctly).
This (unscientific) experiment suggests to me that the cones do more than isolate the TT base, they 'transfer' the 'airborn' vibration that the base was picking up from the music to the target stand. After seeing that the TT would mistrack when the cones were upside down, and not when the TT sat on a towel, it would be hard to argue that the cones were not 'transfering' energy from the stand to the TT base.
I dont understand why it is so hard to imagine that it is possible for vibration to be transfered from one object to another. If its just 'isolation' thats taking place, where does the energy go?