I don't think you are doing anything wrong. I also foster cats and dogs. All of the kittens we rescued were actually born in a feral colony and turned out great, not affraid of anyone. I think a lot of it has to do with most of the kittens came into my house at only a few days old and grew up with a lot of hussle and bussle...and barking. We never have visitors either and the only exposure to other people that my foster cats get is at adoptions. They don't like being at adoptions, but all of the barking dogs doesn't bother them since they live with that at home.

People just need to understand that being at adoptions is stressful on cats and they aren't going to be the freindly cuddle bugs that they are at your house. I try to post signs at adoptions telling people this. I also hang pictures of the cats on their cages that show how they really are at home just to give people an idea of their true personality.

Hope this helps. Don't be so discouraged. You're doing a great thing by providing temporary homes and TLC to these cats that may have died on the streets or in a shelter. Keep up the great work, those babies need it.