Notes prompted by a conversation, but not in direct response to anything therein.
I have not seen obvious invitations for web sites used much recently, but that could be me not looking for web applications to try. I note three three overlapping purposes when they are used:
- Promotion. The entity that has set up the invitation system hopes for viral spam; some people have a strongly negative reaction to invitation systems as a result.
- Rationing. For example, to keep a system usable while resources added.
- Exclusivity. For purposes regarded as wrong for non-state actors (e.g. discrimination based on birth location) to the suspicious (supposed cabals) to the practical (privacy, working group size, keep out bad actors).
My impression is that at the web site/application level, invitations are used mostly for promotion, a little for rationing, rarely for exclusivity. But invitations are ubiquitous in human interactions, and it seems to me that exclusivity is their main purpose (though I’m ignoring many communications and social purposes independent of the three mentioned; e.g., in some situations a polite communication takes the form of an invitation). One doesn’t even need to step away from “social network” web applications to see this, just into the applications — consider “connection requests” and similar actions among users.
Invitations could be a useful part of the federated social web mix, as the challenges faced by federated sites are at least a little different than those faced by silos in all three of the aforementioned areas, but especially with regard to exclusivity. Consider that bad actors can set up their own federated sites, and that federated sites often represent single users or small communities — roughly requiring the same functionality of a community or individual user of a silo, including the functionalities of the entire silo.