Wet ones use Benzethonium Chloride as the active disinfectant, carried in a base that includes alcohol. Thus, as noted on their web site, http://www.wetones.com/Faqs.aspx, they cannot be dried out and then rehydrated for use. However, like Erik, I have found that they are quite effective, and don't contribute much weight. A few wipes, along with a few paper towel pieces make up a nice kit for longer trips out, and, for me, really do make a difference in comfort. The single wipe packaging burns well, and the 15 pack package is fairly weight efficient already. There are some wipes that are sold dry, and intended to be wet before use, but I have not found them to be as effective, and they left me with a lasting fragrance on my skin. If you want to get the disinfecting properties of Benzethonium Chloride without a wipe, it is available in small bottles as well. The advantage of this material is that it, in theory, provides longer lasting disinfecting than alcohol.
Jim