Cable elevators

If you have synthetic rug flooring, then you should keep them off the floor. If you have natural wool, cotton or wood flooring, I wouldn't worry about it. Aside from that, you can make your own or buy something similar to what you see in the ads for a considerable savings. Use your imagination.

In my case, I have my speaker cable looped around a nail in the wall behind the speaker from which hangs a wool carpet (for sound absorption). Looks fine to me. 

All the best,
Nonoise

audiofool1, unless someone's playing basketball on your wooden floors, I don't see any problem. That, and anything you prop them up on will simply transmit the vibrations up to the cables, opening another can of worms. 

All the best,
Nonoise