A method of performing real-time communications over a computer data network between at least two users, each of said at least two users being associated with a client system communicably coupled to said computer data network, comprising the steps of: receiving, at a visibility server system (14, 18) configured to determine instantaneous availability of system users, communicably coupled to said computer data network, a request for a real-time group action involving a group of users, each user having at least one condition associated therewith, a status of the condition associated with each user being indicative of an availability of the user for participating in the real-time group action, wherein the availability of each user is based at least in part upon a digital indication of an online presence of the respective user; in a first determining step, in response to the request, determining the status of the condition associated with each user within the group; in a second determining step (52, 58), determining whether the real-time group action can be performed based at least in part on the status of the condition associated with each user within the group; in a third determining step, in the event the real-time group action cannot be performed based on the status of the condition associated with at least one user within the group, the condition status indicating that the at least one user is unavailable to participate in the real-time group action, determining (54, 55, 56) at least one user to substitute for the at least one unavailable user within the group; in a fourth determining step, determining the status of the condition associated with each user within the group including the at least one substitute user; in a fifth determining step (55, 56, 58), determining whether the real-time group action can be performed based at least in part on the status of the condition associated with each user within the group and the at least one substitute user; and in a first performing step, in the event the real-time group action can be performed based at least in part on the status of the condition associated with each user within the group and the at least one substitute user, performing the real-time group action. receiving, at a visibility server system (14, 18) configured to determine instantaneous availability of system users, communicably coupled to said computer data network, a request for a real-time group action involving a group of users, each user having at least one condition associated therewith, a status of the condition associated with each user being indicative of an availability of the user for participating in the real-time group action, wherein the availability of each user is based at least in part upon a digital indication of an online presence of the respective user; in a first determining step, in response to the request, determining the status of the condition associated with each user within the group; in a second determining step (52, 58), determining whether the real-time group action can be performed based at least in part on the status of the condition associated with each user within the group; in a third determining step, in the event the real-time group action cannot be performed based on the status of the condition associated with at least one user within the group, the condition status indicating that the at least one user is unavailable to participate in the real-time group action, determining (54, 55, 56) at least one user to substitute for the at least one unavailable user within the group; in a fourth determining step, determining the status of the condition associated with each user within the group including the at least one substitute user; in a fifth determining step (55, 56, 58), determining whether the real-time group action can be performed based at least in part on the status of the condition associated with each user within the group and the at least one substitute user; and in a first performing step, in the event the real-time group action can be performed based at least in part on the status of the condition associated with each user within the group and the at least one substitute user, performing the real-time group action.