If Sharecg had a store I probably would submit a few models to sell, and it would depend on what percentage I would get as commission. However the majority of what I use this site for would still be for my free stuff.. I still think its important for me to keep sharing as much as I can allow. Sharecg is the only site where I share my work. At the moment I only create a small amount of work to sell at my Daz store.
If I was to purchase a product here I would want to be sure that what I paid for would work properly, so you would need to show some kind of quality control and testing when taking products for a store.
So long as having a store doesn't diminish the amount of free work being submitted - I cant see the harm in having a store section on the site.