An alternative, complementary version of this article is available here. It's an older version of the same concept that I couldn't quite reconcile in a single article.
Either a subsidiary of FOMO, a conclusion of the Web's current state of hyperconnectivity, or perhaps even both, channel hoarding refers to the act of massively joining of several online chatrooms way beyond the upper limit of personal attention to the communities surrounded around them and the users that comprise them, as per dictated by Dunbar's number. The end result is an inability to properly keep track of every channel in a timely manner causing perpetual idling, the inability to stay up to date or efficiently participate in these communities, and an eventual FOMO feedback loop in which the user feels compelled to fixate in the increasingly impossible task of being an active member of all channels concurrently to the detriment of other, more constructive online social activities.
With a multitude of IRC networks and an almost endless branching of channels dedicated to online communities, hobbies or activities, alongside the association of several channels with each other due to an overlap in users and/or said communities, it becomes very easy to set up several channels in your IRC client's autojoin list. While idling is a common practice in IRC, the act of having a client1) connected 24/7 to these servers contributes very little to both the user and the community, aside from practical reasons such as acquiring chatlogs or keeping a public presence in a channel in order to be easily contacted by someone else. Keeping attention of several dozen channels, active or not, becomes impossible during normal online activities. The effect is twofold, personal and social: on one hand, the hoarding user is impaired of passively reading interactions in each channel, let alone being able to participate in them, thus one of the main reasons of joining a channel in the first place -introducing oneself in an online community- becomes moot. On the other hand, idling (unintentional such as in the case of hoarding or intentional for the reasons described above) quantitatively reduces channel activity in comparison to total users and overall yields to an inertia of inactivity, contributing to the “death” of a channel, i.e. perpetual idling of all its users, with only sporadic conversations that die off into the years.
Without a directed reason to accumulate so many channels, without an aim beyond mere participation, it becomes inevitable to feel a pariah by one's own inaction - but can one be a pariah without providing meaningful participation? Indeed, it is as though you never joined at all!
The decline of IRC as a supplementary gathering spot for online communities is concomitant with the rise of platforms such as Discord. Discord's plethora of features that stand out over irc and its simple2) functionality of “multiplayer notepad” paves the way for Discord servers becoming communities in and of themselves, without the need of a parallel platform such as a website or forum. While this was also present in IRC, as several channels were the result of ad-hoc online gatherings that took a social life of their own or diasporas that kept a group of users together, bound by social ties and by use of the platform, Discord has streamlined the process through “servers” that carry a conversational life of their own through the platform's versatility in both creation and management of commuinities. Discord invites rather than forum links are the ones being passed around between netizens, centralizing online social activity in a single service but carrying with it the same conceptual limitations of a text-oriented centralized chat service, from which channel hoarding emerges.
While it would be more aptly called “server hoarding” in Discord's cases, as each joinable element in it is called a “Server”, the problem of “hoarding” permanence in each of these servers becomes more pronounced as each server can each hold a rather absurd maximum of five hundred “channels”, which are themselves self-contained from the other channels and may be so different from each other that only users are the common element3). A Discord server with several channels is harder to keep track than a single IRC channel unit, and many servers suffer the issue of having too many channels, ostensibly for keeping discussion topics well-separated from each other but causing the server highly susceptible to communicative (and, therefore, userbase) segregation. While a channel in a Discord server is not wholly akin from an independent IRC channel, 10 servers with 10 channels each is definitely much harder to keep track of than 10 IRC channels!
The issues with channel hoarding described above become more evident and more troublesome than with IRC: while IRC is (or was, depending on how dead you consider IRC to be…) usually supplementary to a larger community originated or at least centralized elsewhere, Discord servers are the opposite: more often than not, they are by themselves communities and behave themselves as such - therefore, missing out on the activities Discord server because of being in too many of them to successfully keep track, becomes much more tangibly equivalent to missing out on the activites of an entire community. Hoarding, in this case, directly hampers online participation (or even observation, if the bulk of servers move too quickly for a single person to handle).
There is no complete solution to the hard limits to the ability of keeping track with real-time conversations and community happenings; even as a total hermit, active 24/7 monitoring of participating communities becomes impossible to handle. It's wise to cut losses and prune your existence from channels/servers in which you haven't made a presence for yourself, do not intend to make a presence for yourself (an activity which takes time, effort, and formation of social connections with other users) and provides little for your interest. A compromise, or perhaps a starting step, would be to categorize channels between those of high and low activity, so as to not only figure out which communities are simply occupying mental real estate and even which ones are dead entirely.
All that said, channel hoarding more often than not is the result of a symptom of online FOMO. It's important to deal with the root cause as much as the obstacles created by it in order to enjoy a proactive, healthy and fulfilling online experience.