Yes, but I think the OP was suggesting that the network effect to support a platform is much smaller than most people would think. Consider all the topical sites running PHPBB forums, for example. There are many thousands of vibrant communities around the internet, and they can all coexist peacefully. Many of them feature adds & commercial partnerships, too, and guess what? The click-through and performance of those things is relatively off-the-charts because they directly relevant to the captive audience's interests... especially if representatives from the advertisers directly participate in the community, which many do, and even moreso if the community + advertisers offer IRL community events (which many do).
Besides the depth and stickiness of topical communities, these sites also tend to be almost universally friendly and helpful, even to n00bs and outsiders. It would be a tragedy if they were to be replaced by a one-size-fits-none platform.
Besides the depth and stickiness of topical communities, these sites also tend to be almost universally friendly and helpful, even to n00bs and outsiders. It would be a tragedy if they were to be replaced by a one-size-fits-none platform.