I am also thinking that, in the future, we might allow to put tabbles inside other tabbles (in addition to files). _______For example, you may put tabble "Mary" into tabble "Friends"._____ Then we could enlarge tabbles which contain other tabbles. So "friends" would be larger than "mary". That might be a better criterion for deciding the size of tabbles.
This way tabbles would become a generalization of categories.