Perhaps I should've specified: I was actually referring the the rear cog only. Having triple chain-rings makes sense; it provides a tremendous range and since the rings are larger/thicker they typically last a long time. But is there really much functional difference between 24,27, or 30 gears?
Keep in mind, my perspective is as commuter/tourer, not a racer or cargo-hauler. Again, keep in mind that most riders only use 8-10 gears the vast majority of time. Most only need a couple low gears for inclines, a few mid-range gears for level terrain, and a few higher gears for moderate declines. 24 gears seems perfectly adequate.