I believe that it is good for a child to have a special toy that is all his own. A toy that he does not have to share with others unless he is willing to.
In my opinion, when sharing is mandated, children are really not learning the value of sharing. (I liken this to the concept of the "mandatory donation." Is it really a donation if it's obligatory?) However when a child shares a cherished toy with someone who is entrusted with the care of this prized object, then something special has just happened between two people. The difference here is that the child has made the choice to share.
Maybe if you show this post to your wife, she will reconsider her position. The key here is to teach your children humane values and to figure out how to transmit these values to your kids in a way that doesn't polarize you as parents. I'm not saying that this is what is happening here, but maybe you can combine your viewpoints and find a workable solution. Perhaps you can have community toys along with special toys in your home. It is also important to understand that some toys are not age-appropriate to share, since younger kids may not know how to handle expensive electronic toys with the care that is required.
Suggestions for how to come to a consensus on important family issues can be found in my parenting book
