1. A method of providing a shared history of transactions occurring between two or more members of an interaction group, each member of the interaction group being associated with a respective member machine for interacting with one or more other members through their respective member machines over a network, the method comprising: observing a transaction between two or more members of the interaction group, at least one of the members being currently online with respect to the network, the transaction originating from a member that is currently online with respect to the network; automatically storing a reference to the transaction in a group history file; synchronizing the group history file for all member machines.