To be honest, this is a problem for FriendFeed to deal with. Users have the right to use the services however they want. People's use of a tool can be influenced by what other tools do with the information, but if a user is going to stop sharing because it has been shared “enough” on FriendFeed, then I have a problem with it. FriendFeed should be aggregating the shares from each service, like all reader shares together and all stumbles together. FriendFeed has caused the problem, not the user. The user can choose not to share certain services as well if they feel it does not add value.