I wondered about this as well. I have an AL frame bike from 2005 and it has a carbon seatpost. I am currently in the market for a carbon bike and had assumed they would all be equipped with carbon seatposts. I was surprised at how many carbon bikes have alloy seatposts. Why was such a big deal made out of having the "vibration dampening" properties of the carbon seatpost back in 2005? Was I fed a line of crap back then, or does it just not matter when the rest of the frame is carbon already?