Originally Posted by Wogster

The whole idea with adding more cogs is to make it easier to stay within the 80-95 RPM power band. Up until 8 speed it was often practical to have 2 or 3 freewheels with different ranges, and you selected the appropriate one. Racers in a race like the TdF would have one for the flat stages, another for mountain stages and probably a third for intermediate stages.

The question though, is 11 speed practical, the chains are thinner and narrower, meaning they wear out faster, some people say a lot faster, and they cost more to replace. The cogs also wear faster, and are more expensive to replace. I doubt many people would notice a very large performance change between 10 and 11 speed, unless they race and a hundredth of a second is a big deal.