Can anyone explain cable risers?

"Funny MY cable risers are empty toilet paper rolls."

Elizabeth, you are a Paragon of practicality. You can even make nonsense sound sensible.
Cheers

"You can bet your bottom dollar that NONE of the various recording/mixing/mastering facilities are suspending their cables during the making of a recording."

I like that answer. All the recording studios I've worked in had the cables bundled together running across the floor or up inside a drop-ceiling. (We did keep power cables away from audio).
But I would agree with the theory to keep cables off the carpet.

Use gold coins below your cables and you will hear the improvement
immediately. Gold gets in reaction with the electrical field of the cables
and improves the molecular flow (more shiny). Some say, the best are
Krugerrands from South Africa ... but after long research I finally settled
with white-gold Rolexes below my cables. There is a swiss precision
added to details which is unique ...

Nonoise,
I agree with your statement concerning the effect of synthetic carpet. When my cables are lifted off that surface there`s an improvement in clarity,or as you say less smearing. The change is subtle but consistent.I can`t comment on other flooring materials.
Regards,

There is a firm, scientific basis for raising cables off of the carpet changing the way that electrons flow through them. The carpet actually acts as part of the dielectric covering the conductors:

http://en.wikipedia.org/wiki/Dielectric

Taking the cables out of contact with the dielectric of the carpet will hence change the electron flow and fields within the cable.

Of course, the audibility of all this is up for discussion. Personally, my life is too short. But I would never dismiss the idea.