There are two schools of thought. One says that you should couple the speaker to the stand to help drain away un-wanted energy. The other says that the speaker should be de-coupled from the stand.
I suspect that each approach works in different situations ie. You don't want to transmit vibrations into a suspended floor.
Isolation requires either something like the Auralex Gramma, or Sorbathane / blu-tak or Herbie's Fat dots.
It is generally accepted that spikes actually couple the speaker to the stand (which isn't necessarily a bad thing). Back in 09, when Keith Howard used an accelerometer to measure vibration, he discovered that vibration in the speaker stand was 100 times greater using cones vs rubbery feet.
In case you are interested here is an article;