Bi-Wiring can be helpful when/if you have a very long length of cable to run. Essentially, the most important thing about speaker wire is impedance(resistance), the lower the gauge (thicker the cable) the less resistance you will have(a good thing). Lower gauge cable is more expensive and harder to run sometimes, not to mention if it is too big around, you won't be able to connect it to the binding posts. Bi-Wiring has the cumulative effect of lowering the resistance without having to buy super low gauge wire. However, most set-ups won't require this. The first link below has a table for gauge recommendations for runs.
A good article on speaker gauge recommendations for Resistance/Distance:
http://www.audioholics.com/education/cables/speaker-cable-gaugeAn article that goes in depth about bi-wiring, and why it has little/no measurable effect on sound:
http://www.audioholics.com/education/cab...erm=bi%20wiring
