No Community Can Do Everything: Why People Participate in Similar Online Communities

1. Problem Statement

While large-scale quantitative studies have established that users frequently participate in multiple, overlapping online communities (both within and across platforms) and that these overlaps share similar topics and memberships, there is a significant gap in understanding why this occurs from the user's perspective.

• The Gap: Existing research relies heavily on computational analysis to describe that overlaps exist and their ecological consequences (e.g., growth rates, competition). However, there is little empirical evidence explaining the emic (insider) motivations behind why individuals choose to participate in multiple, similar communities simultaneously.
• The Core Question: Why do the same individuals talk to each other about similar things in different online spaces? Why do overlapping communities persist rather than consolidating into a single dominant group?

2. Methodology

The authors employed a qualitative, grounded theory approach to complement existing quantitative literature.

• Data Source: Reddit, a platform characterized by low barriers to entry for creating sub-communities ("subreddits"), leading to high topic and user overlap.
• Participant Selection:
  • Cluster Identification: The authors analyzed the Pushshift Reddit dataset (comments prior to April 2020) for the top 10,000 subreddits. They used TF-IDF cosine similarity and Affinity Propagation clustering to identify groups of subreddits with highly overlapping users and topics.
  • Visualization: They created a t-SNE visualization to manually select interest-driven clusters (excluding sensitive topics like politics or pornography).
  • Recruitment: From nine selected clusters (covering topics like rock climbing, drag culture, indie music, vintage audio, etc.), they recruited 20 active participants. Criteria included being an adult, English-speaking, and active in multiple subreddits within a cluster for at least one year.
• Data Collection: Semi-structured interviews (average 49 minutes) conducted via Zoom, phone, or Discord.
• Analysis: The team used Charmaz's grounded theory approach. They conducted iterative coding (generating 950+ codes) and axial coding to develop 18 thematic memos, moving from inductive data collection to theoretical abstraction.

3. Key Contributions

The paper's primary contribution is a theoretical framework explaining the structural limitations of single online communities and the resulting necessity for ecosystems of overlapping communities.

• The "Trilemma" Framework: The authors propose that users seek three distinct benefits from online communities, but these benefits are mutually incompatible within a single community structure. A single community can typically provide only two of the three, forcing users to participate in a "portfolio" of communities to satisfy all needs.
  1. Specific Content: Access to niche information, specialized discussions, and expert advice.
  2. Homophily: Socialization with similar others (shared identity, demographics, expertise, or status).
  3. Largest Possible Audience: Maximum visibility and attention for one's contributions.
• Reframing Ecological Concepts: The study challenges the application of "competition" in social computing ecology. Instead of viewing overlapping communities as competitors, participants view them as mutualistic and complementary. The ecosystem functions through resource partitioning, where different communities specialize in different subsets of the user's needs.

4. Key Results & Findings

A. The Three Benefits and Their Tensions

The study identified three specific tensions (trade-offs) that prevent a single community from satisfying all user needs:

1. Audience Size vs. Specific Content (The "Background Noise" Problem):

   • Large communities (e.g., r/climbing, r/podcasts) offer massive reach but suffer from high volumes of low-effort or generic content ("background noise").
   • Users seeking highly specific advice (e.g., reel-to-reel audio repair) must move to smaller, niche subreddits (e.g., r/ReelToReel) where expert density is high, even if the total audience is small.
   • Result: Large audiences dilute the quality and specificity of information.

2. Audience Size vs. Homophily (The "Big City" Effect):

   • Large communities often feel impersonal, anonymous, and "rushed," resembling a busy city where people do not have time to chat.
   • Smaller communities foster repeated interactions, trust, and a sense of belonging ("finding my people").
   • Result: As a community grows, the ability to form deep, homophilous social bonds decreases.

3. Specific Content vs. Homophily (The Diversity Paradox):

   • Highly specialized, homophilous groups (e.g., a group of only experts) may lack the diversity needed for certain types of learning or cultural exchange.
   • Conversely, strict rules in specialized groups to maintain content quality often stifle the off-topic socializing that builds community.
   • Result: Users often need a "main" community for broad discussion and a "jerk" or "meta" community for off-topic socializing, or they need diverse groups to learn from outsiders.

B. The "Trilemma" Visualization

The authors visualize this as a Venn diagram where:

• Area A: Large Audience + Specific Content (but low homophily).
• Area B: Large Audience + Homophily (but low specific content).
• Area C: Specific Content + Homophily (but small audience).
• Center: No single community exists that occupies the intersection of all three.

C. User Perception of Competition vs. Mutualism

• Competition: Participants rarely perceived their communities as competitors. They viewed moderator conflicts as rare and structural competition as non-existent.
• Mutualism: Participants overwhelmingly described the relationship between overlapping communities as mutualistic. They saw different subreddits as "niches" that fit together to form a complete ecosystem. For example, a user might post in a large subreddit for visibility and a small one for feedback, viewing them as complementary rather than competing for the same "resources."

5. Significance and Implications

• Theoretical Impact: The paper moves social computing theory from a purely quantitative/ecological view (focusing on growth/survival metrics) to a qualitative understanding of user agency. It suggests that the proliferation of overlapping communities is not a failure of consolidation but a successful adaptive strategy by users to navigate the "trilemma" of online participation.
• Ecological Theory Application: It validates and expands Resource Partitioning Theory (RPT) from organizational science to digital spaces. It posits that as a generalist community grows, it becomes too heterogeneous to serve niche needs, leading to the emergence of specialized "generalist" and "specialist" sub-communities.
• Design Implications:
  • Platform Design: Platforms like Stack Exchange that prohibit overlapping communities may be limiting the range of benefits they can offer. Reddit's model of allowing low-cost creation of overlapping spaces is shown to be beneficial for user satisfaction.
  • Discovery Tools: Recommendation algorithms should not just suggest the "largest" community but should help users build a portfolio of communities (e.g., suggesting a niche community for specific advice and a large one for visibility).
  • Cross-Community Tools: Features like "multireddits" are currently cumbersome. Better tools for cross-posting and linking between related communities could help users manage their portfolios more effectively.

Conclusion

The paper concludes that "No Community Can Do Everything." The existence of overlapping, similar communities is a rational response to the inherent trade-offs between audience size, content specificity, and social homophily. Users actively construct portfolios of communities to maximize the total utility they derive from online participation, creating a mutualistic ecosystem rather than a competitive one.