I have conducted a scientific study of shoe trees that is now ready for publication here on The Style Forum. During the study, I used 4 pairs of shoes: a brown C&J Savile, a black C&J Whitehall, a brown C&J Whitehall, and a black C&J Aintree. I used all C&J shoes for this study to set equal the leather variables used. Over a 120-day period, I wore each shoe once every four days for a 12 hour period. Upon removal, I placed cedar Zappos shoe trees in the brown Savile and the black Whitehall. The brown Whitehall and the black Aintree were left without trees for the duration. Here are my findings: The shoe-tree treated shoes experienced a 17% reduction in wetness within 24 hours of having the shoe trees placed in them after wear. After 3 days, the level of wetness had dissipated. The shoes also experienced a .12% increase in width do to the stretching factor of the shoe trees, though this was undetectable unless wearing cashmere socks which tended to slide in the shoe and increase wetness significantly (See TDial, J, Fabienne, 1.23.05, "Cashmere Wetness Study"). The untreated (un-"tree"ted, if you will) shoes experienced a 12% decrease in wetness over the first 24 hours due to air drying and Bernese Mountain Dog tampering (dog may have actually added wetness due to slobbering mouth, though slobber level was not measured). After 3 days, the wetness had also dissipated to an undetectable level. Shoes experienced a .12% decrease in overall width due to the air drying of the leather. Overall, though the findings were someone inconclusive, due to the fact that I only actually own three of the mention shoes and the black Aintree is only a dream, we recommend buying shoe trees for all shoes. Scientifically speaking, it's better to be safe than sorry and the added weight of the shoe tree in the shoe makes it very difficult for small and large breeds of dog to carry away to other parts of your dwelling. I hope you find this helpful.