HELP! My Friendship bread starter is multyplying faster than rabbits and gremlins in a contest!?

I have allready given starters to my friends. Now I have them reproducing in my freezer. How can I keep just one starter for myself to perpetuate the 10 day cycle without all the excess ones? My friends won't answer their doors anymore lol! I think it should be called "Get Even Bread" instead of "Amish Friendship Bread" lol!