As mentioned, spikes reduce the contact surface and form a more rigid coupling to the floor. A simple experiment can illustrate this--take a telephone book (the bigger the better). Slide it on a smooth surface. Then tape three pennies on the bottom and slide it on the pennies. Reducing the surface area increases the friction and makes it harder to move. As to the second part about disapating energy through spikes, the theory is correct, but I don't think in practical terms it is very effective. Disapating energy is best done with devices designed to do just that. I have a few of these made by Teknik (I think), but I don't think they work very well. The theory is they convert the vibrational energy into heat energy.
Why is coupling the speakers to the floor important? You increase the effective mass of the speaker. This is important for accurate bass reproduction (which intail effects the entire frequency spectrum). The bass driver in your speaker works like a piston moving back and forth. You may have heard "for every action there's an equal and opposite reaction" (I didn't make that up--Newton did). If the speaker can move about it will, and thus the force that bass driver is exerting is reduced by the movement of the speaker. If the speaker is coupled to the floor it can not move as easily, and thus the bass driver works more effectively. Not to belabor the point--there is still an equal and opposite reaction, but now the mass has increased as the speaker is coupled to the floor, so the movement is much smaller.
The effect of spikes will change depending (mostly) on a combination of speaker weight and the bass driver. Therefore a realtively large speaker with only 5 inch drivers will not benefit as much as either a mini monitor or a large speaker with a large (12 inch) driver.
In the end Argent said it right--try it,