[MrFlippant]

Pooh to silicones....noisy, hard to true, hard to glue, imcompatible with any other material....

While I agree, and prefer other materials as well, it's only fair to point out that silicone tires have good grip on clean tracks, are hard wearing so rarely need replacement, don't "melt" or harden over time, cannot be treated with any "magic potion" chemicals, and are readily available for most wheels out there from a variety of makers. 

They're only "bad" when other compounds are being used on the same track. For example, one of the guys in my analog club has a wood track, which we race on usually once every other month. He knows very little about car tuning, and usually has one of the other guys do his cars for club races. But, he pretty much puts new silicone tires on every new car he gets, and we often run his cars for the IROC race at his track. Even though he sees what happens when we practice on rubber, then run IROC on silicone, and have terrible traction for the race we then conduct, he gets upset when anyone points out this unavoidable result when silicone is used on the same track. It's a great track, so we just deal with it every other month.